<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e4af3-cd9b-70cd-9270-77d98dd96870,g:e40f17cc-376e-472b-b368-681c22da8a9a-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://accelerant.ai/role/CoverPage" xlink:type="simple" xlink:href="arx-20260630.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019e4af3-d29f-7a68-a765-97add39a6e70" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentInformationTable_019e4af3-d29f-7a68-a765-97add39a6e70" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7ae6-a6ff-6cb1746b06b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019e4af3-d29f-7a68-a765-97add39a6e70" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7ae6-a6ff-6cb1746b06b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-7ae6-a6ff-6cb1746b06b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7ae6-a6ff-6cb1746b06b4" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-7ae6-a6ff-6cb1746b06b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-708f-b1c2-5faf3d685171" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7ae6-a6ff-6cb1746b06b4" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-708f-b1c2-5faf3d685171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4af3-d29f-7e73-92c1-1f3ed9958801" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-708f-b1c2-5faf3d685171" xlink:to="loc_us-gaap_CommonClassAMember_019e4af3-d29f-7e73-92c1-1f3ed9958801" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4af3-d29f-7106-acb1-9446f1bfdf37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-708f-b1c2-5faf3d685171" xlink:to="loc_us-gaap_CommonClassBMember_019e4af3-d29f-7106-acb1-9446f1bfdf37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019e4af3-d29f-7fee-94c7-1dcd85fb57a8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentType_019e4af3-d29f-7fee-94c7-1dcd85fb57a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019e4af3-d29f-708d-8775-946279606e36" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentQuarterlyReport_019e4af3-d29f-708d-8775-946279606e36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019e4af3-d29f-7868-a013-b7d87d6195ba" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentPeriodEndDate_019e4af3-d29f-7868-a013-b7d87d6195ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019e4af3-d29f-7f53-be04-f9d57b694f33" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentTransitionReport_019e4af3-d29f-7f53-be04-f9d57b694f33" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019e4af3-d29f-7c4c-9cbc-367f97560384" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityFileNumber_019e4af3-d29f-7c4c-9cbc-367f97560384" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019e4af3-d29f-74a4-8b2b-7894491b750c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityRegistrantName_019e4af3-d29f-74a4-8b2b-7894491b750c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019e4af3-d29f-7ccb-98f2-ea6b2eff8f51" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019e4af3-d29f-7ccb-98f2-ea6b2eff8f51" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCountry_019e4af3-d29f-7625-ad1c-078a5941f551" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCountry"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityAddressCountry_019e4af3-d29f-7625-ad1c-078a5941f551" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019e4af3-d29f-714b-a768-63b2608bb455" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityTaxIdentificationNumber_019e4af3-d29f-714b-a768-63b2608bb455" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019e4af3-d29f-7aeb-a378-06ebb58bffd1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityAddressAddressLine1_019e4af3-d29f-7aeb-a378-06ebb58bffd1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019e4af3-d29f-7a4b-806a-679148d66db0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityAddressAddressLine2_019e4af3-d29f-7a4b-806a-679148d66db0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine3_019e4af3-d29f-7bea-8520-c5fe29f669ea" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityAddressAddressLine3_019e4af3-d29f-7bea-8520-c5fe29f669ea" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019e4af3-d29f-7d35-bdf2-0dc19ff9ebef" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityAddressCityOrTown_019e4af3-d29f-7d35-bdf2-0dc19ff9ebef" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019e4af3-d29f-7e3b-9be1-46e3f4d605d8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityAddressPostalZipCode_019e4af3-d29f-7e3b-9be1-46e3f4d605d8" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019e4af3-d29f-7a08-99cf-399a31f2db21" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_CityAreaCode_019e4af3-d29f-7a08-99cf-399a31f2db21" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019e4af3-d29f-705b-b085-0cca14cf27b0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_LocalPhoneNumber_019e4af3-d29f-705b-b085-0cca14cf27b0" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019e4af3-d29f-7531-90d0-8a1230a17a7e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_Security12bTitle_019e4af3-d29f-7531-90d0-8a1230a17a7e" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019e4af3-d29f-7a82-a22e-4ac1f1572504" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_TradingSymbol_019e4af3-d29f-7a82-a22e-4ac1f1572504" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019e4af3-d29f-70f4-b465-ec82a8c3dc92" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_SecurityExchangeName_019e4af3-d29f-70f4-b465-ec82a8c3dc92" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019e4af3-d29f-779c-8ec4-77a7d45d4745" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityCurrentReportingStatus_019e4af3-d29f-779c-8ec4-77a7d45d4745" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019e4af3-d29f-7505-81dd-cc798377c563" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityInteractiveDataCurrent_019e4af3-d29f-7505-81dd-cc798377c563" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019e4af3-d29f-75c6-8ad1-e3d90ebab4b1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityFilerCategory_019e4af3-d29f-75c6-8ad1-e3d90ebab4b1" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019e4af3-d29f-7d96-a64f-179a5bf76123" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntitySmallBusiness_019e4af3-d29f-7d96-a64f-179a5bf76123" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019e4af3-d29f-7d36-9264-19cd9adec5e6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityEmergingGrowthCompany_019e4af3-d29f-7d36-9264-19cd9adec5e6" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_019e4af3-d29f-7372-bffa-ee1eb3fed474" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityExTransitionPeriod_019e4af3-d29f-7372-bffa-ee1eb3fed474" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019e4af3-d29f-7a31-a503-8a6165b803a8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityShellCompany_019e4af3-d29f-7a31-a503-8a6165b803a8" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019e4af3-d29f-7188-a995-0b6ad1853629" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019e4af3-d29f-7188-a995-0b6ad1853629" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019e4af3-d29f-7214-a3d4-98b1995467d3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_AmendmentFlag_019e4af3-d29f-7214-a3d4-98b1995467d3" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019e4af3-d29f-70b3-b95a-9d51d6146bc9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_CurrentFiscalYearEndDate_019e4af3-d29f-70b3-b95a-9d51d6146bc9" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019e4af3-d29f-7b67-a089-a692edda48ec" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentFiscalYearFocus_019e4af3-d29f-7b67-a089-a692edda48ec" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019e4af3-d29f-7cf0-99d2-b3e559bb17b8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019e4af3-d29f-7cf0-99d2-b3e559bb17b8" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019e4af3-d29f-778f-a0b9-b22f1d86947a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019e4af3-d29f-78c9-9571-9c984297f3c9" xlink:to="loc_dei_EntityCentralIndexKey_019e4af3-d29f-778f-a0b9-b22f1d86947a" xlink:type="arc" order="31"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/CondensedConsolidatedBalanceSheetsunaudited" xlink:type="simple" xlink:href="arx-20260630.xsd#CondensedConsolidatedBalanceSheetsunaudited"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/CondensedConsolidatedBalanceSheetsunaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4af3-d29f-7b53-a7a2-223b631eebd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4af3-d29f-7ac8-b0ac-e9b61571be0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-7b53-a7a2-223b631eebd4" xlink:to="loc_us-gaap_StatementTable_019e4af3-d29f-7ac8-b0ac-e9b61571be0c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-77ab-9881-1ce96995ff2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4af3-d29f-7ac8-b0ac-e9b61571be0c" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-77ab-9881-1ce96995ff2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-77ab-9881-1ce96995ff2e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-77ab-9881-1ce96995ff2e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-77ab-9881-1ce96995ff2e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7bdd-9cb2-f928f433d78f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-77ab-9881-1ce96995ff2e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7bdd-9cb2-f928f433d78f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_DebtSecuritiesAvailableForSaleShortTermInvestmentsMember_019e4af3-d29f-7541-8625-1595f10e2643" xlink:href="arx-20260630.xsd#arx_DebtSecuritiesAvailableForSaleShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7bdd-9cb2-f928f433d78f" xlink:to="loc_arx_DebtSecuritiesAvailableForSaleShortTermInvestmentsMember_019e4af3-d29f-7541-8625-1595f10e2643" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019e4af3-d29f-7f85-a8b8-4a2971174ecb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7bdd-9cb2-f928f433d78f" xlink:to="loc_us-gaap_FixedMaturitiesMember_019e4af3-d29f-7f85-a8b8-4a2971174ecb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-7b53-a7a2-223b631eebd4" xlink:to="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsAbstract_019e4af3-d29f-79f6-9357-1afe0ec82bb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_InvestmentsAbstract_019e4af3-d29f-79f6-9357-1afe0ec82bb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d29f-7f3f-b279-f180592655b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAbstract_019e4af3-d29f-79f6-9357-1afe0ec82bb6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d29f-7f3f-b279-f180592655b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019e4af3-d29f-7780-979a-c8b4154ce6a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAbstract_019e4af3-d29f-79f6-9357-1afe0ec82bb6" xlink:to="loc_us-gaap_EquityMethodInvestments_019e4af3-d29f-7780-979a-c8b4154ce6a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d29f-7651-b935-7af7d8958e49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAbstract_019e4af3-d29f-79f6-9357-1afe0ec82bb6" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d29f-7651-b935-7af7d8958e49" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_019e4af3-d29f-7df9-8a76-39537b019a8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Investments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAbstract_019e4af3-d29f-79f6-9357-1afe0ec82bb6" xlink:to="loc_us-gaap_Investments_019e4af3-d29f-7df9-8a76-39537b019a8d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e4af3-d29f-76c0-a4bd-caa64d8dfa07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019e4af3-d29f-76c0-a4bd-caa64d8dfa07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsReceivableAtCarryingValue_019e4af3-d29f-74f8-bd91-0d8c70ca8236" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsReceivableAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_PremiumsReceivableAtCarryingValue_019e4af3-d29f-74f8-bd91-0d8c70ca8236" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidReinsurancePremiums_019e4af3-d29f-744d-bc21-20a629181c0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidReinsurancePremiums"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_PrepaidReinsurancePremiums_019e4af3-d29f-744d-bc21-20a629181c0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments_019e4af3-d29f-7bbe-83d6-a694e3f0c4b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments_019e4af3-d29f-7bbe-83d6-a694e3f0c4b9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ReinsuranceRecoverableForPaidClaimsAndClaimAdjustmentsIncludingDepositAssets_019e4af3-d29f-7261-90f2-ea9b709fabad" xlink:href="arx-20260630.xsd#arx_ReinsuranceRecoverableForPaidClaimsAndClaimAdjustmentsIncludingDepositAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_arx_ReinsuranceRecoverableForPaidClaimsAndClaimAdjustmentsIncludingDepositAssets_019e4af3-d29f-7261-90f2-ea9b709fabad" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCosts_019e4af3-d29f-7808-83f1-64d63b757995" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCosts_019e4af3-d29f-7808-83f1-64d63b757995" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_IntangibleAssetOtherIncludingGoodwillAfterAccumulatedAmortization_019e4af3-d29f-7236-afa3-0e724c450545" xlink:href="arx-20260630.xsd#arx_IntangibleAssetOtherIncludingGoodwillAfterAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_arx_IntangibleAssetOtherIncludingGoodwillAfterAccumulatedAmortization_019e4af3-d29f-7236-afa3-0e724c450545" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_SoftwareInDevelopmentInternallyDevelopedAndPurchased_019e4af3-d29f-7130-935d-4030891ad3f9" xlink:href="arx-20260630.xsd#arx_SoftwareInDevelopmentInternallyDevelopedAndPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_arx_SoftwareInDevelopmentInternallyDevelopedAndPurchased_019e4af3-d29f-7130-935d-4030891ad3f9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets_019e4af3-d29f-7eb1-8d50-54a880d4c6ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssets_019e4af3-d29f-7eb1-8d50-54a880d4c6ed" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e4af3-d29f-7240-94f9-edd388fc7dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4af3-d29f-7272-a9a5-092de6893858" xlink:to="loc_us-gaap_Assets_019e4af3-d29f-7240-94f9-edd388fc7dfe" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-7b53-a7a2-223b631eebd4" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense_019e4af3-d29f-716d-89d7-f8c7595c38d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense_019e4af3-d29f-716d-89d7-f8c7595c38d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnearnedPremiums_019e4af3-d29f-79c1-ade9-757eaab536c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnearnedPremiums"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_UnearnedPremiums_019e4af3-d29f-79c1-ade9-757eaab536c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededPremiumsPayable_019e4af3-d29f-7c91-9cb7-ae0118ba0f56" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededPremiumsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_CededPremiumsPayable_019e4af3-d29f-7c91-9cb7-ae0118ba0f56" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncome_019e4af3-d29f-7097-9dc2-a5c6e45befe6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_DeferredIncome_019e4af3-d29f-7097-9dc2-a5c6e45befe6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FundsHeldUnderReinsuranceAgreementsLiability_019e4af3-d29f-734f-9cf4-c770046d3193" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FundsHeldUnderReinsuranceAgreementsLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_FundsHeldUnderReinsuranceAgreementsLiability_019e4af3-d29f-734f-9cf4-c770046d3193" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e4af3-d29f-77a7-a117-5b3ef77c7c86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_LongTermDebt_019e4af3-d29f-77a7-a117-5b3ef77c7c86" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019e4af3-d29f-7439-87c3-7415c8ac52f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019e4af3-d29f-7439-87c3-7415c8ac52f3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019e4af3-d29f-7eee-9926-c9482bc27231" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_Liabilities_019e4af3-d29f-7eee-9926-c9482bc27231" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019e4af3-d29f-75fd-a5b2-de7b46a95128" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019e4af3-d29f-75fd-a5b2-de7b46a95128" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityAbstract_019e4af3-d29f-77bb-8fb7-f075076d4ecf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4af3-d29f-72f9-842c-32757cd88849" xlink:to="loc_us-gaap_TemporaryEquityAbstract_019e4af3-d29f-77bb-8fb7-f075076d4ecf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TemporaryEquityAbstract_019e4af3-d29f-77bb-8fb7-f075076d4ecf" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019e4af3-d29f-7c85-b29f-953f9240b33c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_CommonStockValue_019e4af3-d29f-7c85-b29f-953f9240b33c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019e4af3-d29f-75e7-ab6f-314526b75d27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019e4af3-d29f-75e7-ab6f-314526b75d27" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e4af3-d29f-7f15-a1ab-b0107ade9eb0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e4af3-d29f-7f15-a1ab-b0107ade9eb0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e4af3-d29f-73c8-a796-d2cb5e398151" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e4af3-d29f-73c8-a796-d2cb5e398151" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e4af3-d29f-7cf7-a580-2cb9cda4f4eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_StockholdersEquity_019e4af3-d29f-7cf7-a580-2cb9cda4f4eb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_019e4af3-d29f-7edd-a81c-2797bccb428b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_MinorityInterest_019e4af3-d29f-7edd-a81c-2797bccb428b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4af3-d29f-755d-b694-ea4f46930119" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4af3-d29f-755d-b694-ea4f46930119" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e4af3-d29f-7111-94a3-a7310903fe3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4af3-d29f-74ee-8a8f-2a8a5b65c1bf" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e4af3-d29f-7111-94a3-a7310903fe3f" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/CondensedConsolidatedBalanceSheetsunauditedParenthetical" xlink:type="simple" xlink:href="arx-20260630.xsd#CondensedConsolidatedBalanceSheetsunauditedParenthetical"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/CondensedConsolidatedBalanceSheetsunauditedParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4af3-d29f-7857-8889-634fdfd8de47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:to="loc_us-gaap_StatementTable_019e4af3-d29f-7857-8889-634fdfd8de47" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-770f-a913-71dd6a987d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4af3-d29f-7857-8889-634fdfd8de47" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-770f-a913-71dd6a987d8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-770f-a913-71dd6a987d8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-770f-a913-71dd6a987d8e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-770f-a913-71dd6a987d8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7afe-a69c-9a012e3c468c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d29f-770f-a913-71dd6a987d8e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7afe-a69c-9a012e3c468c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_DebtSecuritiesAvailableForSaleShortTermInvestmentsMember_019e4af3-d29f-7d46-b882-4c381b894c77" xlink:href="arx-20260630.xsd#arx_DebtSecuritiesAvailableForSaleShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7afe-a69c-9a012e3c468c" xlink:to="loc_arx_DebtSecuritiesAvailableForSaleShortTermInvestmentsMember_019e4af3-d29f-7d46-b882-4c381b894c77" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019e4af3-d29f-7b4b-88a5-c2c606c4729d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d29f-7afe-a69c-9a012e3c468c" xlink:to="loc_us-gaap_FixedMaturitiesMember_019e4af3-d29f-7b4b-88a5-c2c606c4729d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7213-80b7-5371521cff7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4af3-d29f-7857-8889-634fdfd8de47" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7213-80b7-5371521cff7b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-7213-80b7-5371521cff7b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7213-80b7-5371521cff7b" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-7213-80b7-5371521cff7b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-745b-bcf9-b53315acc5bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7213-80b7-5371521cff7b" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-745b-bcf9-b53315acc5bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4af3-d29f-7c98-a4dd-44d7276e3975" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-745b-bcf9-b53315acc5bf" xlink:to="loc_us-gaap_CommonClassAMember_019e4af3-d29f-7c98-a4dd-44d7276e3975" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4af3-d29f-7156-9dda-084b0b748604" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-745b-bcf9-b53315acc5bf" xlink:to="loc_us-gaap_CommonClassBMember_019e4af3-d29f-7156-9dda-084b0b748604" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e4af3-d29f-74c3-a190-7ac38e930727" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e4af3-d29f-74c3-a190-7ac38e930727" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsReceivableAllowanceForDoubtfulAccounts_019e4af3-d29f-7eef-9dfa-e075c09c2fa4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsReceivableAllowanceForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:to="loc_us-gaap_PremiumsReceivableAllowanceForDoubtfulAccounts_019e4af3-d29f-7eef-9dfa-e075c09c2fa4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e4af3-d29f-72f7-9312-93b1ecf413ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e4af3-d29f-72f7-9312-93b1ecf413ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019e4af3-d29f-7475-98cd-519e62842408" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:to="loc_us-gaap_CommonStockSharesIssued_019e4af3-d29f-7475-98cd-519e62842408" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4af3-d29f-73e9-aa61-28f3b01d384d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-731b-b2cf-f318ca789e7b" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e4af3-d29f-73e9-aa61-28f3b01d384d" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/CondensedConsolidatedStatementsofEquityunaudited" xlink:type="simple" xlink:href="arx-20260630.xsd#CondensedConsolidatedStatementsofEquityunaudited"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/CondensedConsolidatedStatementsofEquityunaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4af3-d29f-797e-9d87-d42c5daaf487" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4af3-d29f-7ba5-a5d3-8f60b918bbec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-797e-9d87-d42c5daaf487" xlink:to="loc_us-gaap_StatementTable_019e4af3-d29f-7ba5-a5d3-8f60b918bbec" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d29f-7655-babc-08e94c12c05a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4af3-d29f-7ba5-a5d3-8f60b918bbec" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d29f-7655-babc-08e94c12c05a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4af3-d29f-7655-babc-08e94c12c05a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d29f-7655-babc-08e94c12c05a" xlink:to="loc_us-gaap_EquityComponentDomain_019e4af3-d29f-7655-babc-08e94c12c05a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4af3-d29f-7393-a9fe-3016b16355c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d29f-7655-babc-08e94c12c05a" xlink:to="loc_us-gaap_EquityComponentDomain_019e4af3-d29f-7393-a9fe-3016b16355c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParentMember_019e4af3-d29f-7e88-b812-f18fef0961a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4af3-d29f-7393-a9fe-3016b16355c9" xlink:to="loc_us-gaap_ParentMember_019e4af3-d29f-7e88-b812-f18fef0961a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e4af3-d29f-7345-b1a0-0a16092a73c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019e4af3-d29f-7e88-b812-f18fef0961a8" xlink:to="loc_us-gaap_CommonStockMember_019e4af3-d29f-7345-b1a0-0a16092a73c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019e4af3-d29f-7bde-b8a2-510154d87f0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019e4af3-d29f-7e88-b812-f18fef0961a8" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019e4af3-d29f-7bde-b8a2-510154d87f0a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e4af3-d29f-7e1d-a1fa-06ff7609cd6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019e4af3-d29f-7e88-b812-f18fef0961a8" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e4af3-d29f-7e1d-a1fa-06ff7609cd6d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019e4af3-d29f-7133-9faa-9a0ab2bbd421" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_019e4af3-d29f-7e88-b812-f18fef0961a8" xlink:to="loc_us-gaap_RetainedEarningsMember_019e4af3-d29f-7133-9faa-9a0ab2bbd421" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019e4af3-d29f-7eb5-b24e-2d6d3204490b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4af3-d29f-7393-a9fe-3016b16355c9" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019e4af3-d29f-7eb5-b24e-2d6d3204490b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7980-8a4c-b78c80ee9280" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4af3-d29f-7ba5-a5d3-8f60b918bbec" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7980-8a4c-b78c80ee9280" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-7980-8a4c-b78c80ee9280_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7980-8a4c-b78c80ee9280" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-7980-8a4c-b78c80ee9280_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-72c0-8fb4-d3692944fe94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d29f-7980-8a4c-b78c80ee9280" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-72c0-8fb4-d3692944fe94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredClassAMember_019e4af3-d29f-791b-8086-a01ca27c9fc4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-72c0-8fb4-d3692944fe94" xlink:to="loc_us-gaap_PreferredClassAMember_019e4af3-d29f-791b-8086-a01ca27c9fc4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredClassBMember_019e4af3-d29f-7fbd-9757-651b8ac3c1a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d29f-72c0-8fb4-d3692944fe94" xlink:to="loc_us-gaap_PreferredClassBMember_019e4af3-d29f-7fbd-9757-651b8ac3c1a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_019e4af3-d29f-7e76-9860-95be62aeede9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInTemporaryEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-797e-9d87-d42c5daaf487" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_019e4af3-d29f-7e76-9860-95be62aeede9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_019e4af3-d29f-7ec7-9d0e-25fbebc7662c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_019e4af3-d29f-7e76-9860-95be62aeede9" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_019e4af3-d29f-7ec7-9d0e-25fbebc7662c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_019e4af3-d29f-7fb7-a4c2-410466e6c9b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4af3-d29f-797e-9d87-d42c5daaf487" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4af3-d29f-7d9d-91be-4b7a11c82af4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4af3-d29f-7d9d-91be-4b7a11c82af4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e4af3-d29f-723c-baab-c6578d0b2732" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_ProfitLoss_019e4af3-d29f-723c-baab-c6578d0b2732" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e4af3-d29f-75b0-85d0-a3e49a47262f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e4af3-d29f-75b0-85d0-a3e49a47262f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e4af3-d29f-70d9-b744-4b0b553e7c8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e4af3-d29f-70d9-b744-4b0b553e7c8c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019e4af3-d29f-7209-b826-ce7354f77317" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019e4af3-d29f-7209-b826-ce7354f77317" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019f9985-fd78-7bd7-81ee-c8fd65b3553b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019f9985-fd78-7bd7-81ee-c8fd65b3553b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_019e4af3-d29f-7547-80b3-4e82c7f2c0f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d29f-7ea0-ab48-fcb95cd157a8" xlink:to="loc_us-gaap_StockholdersEquityOther_019e4af3-d29f-7547-80b3-4e82c7f2c0f2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4af3-d29f-7d91-94c6-33361a30daba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/NatureofbusinessandbasisofpresentationDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#NatureofbusinessandbasisofpresentationDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/NatureofbusinessandbasisofpresentationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fc751-b535-704a-9376-3347a37b9f3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fc751-b535-749c-8801-72bbc7609b0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fc751-b535-704a-9376-3347a37b9f3e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fc751-b535-749c-8801-72bbc7609b0e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019fc751-b535-79f0-b1a6-e0bdb800fa7a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fc751-b535-749c-8801-72bbc7609b0e" xlink:to="loc_dei_LegalEntityAxis_019fc751-b535-79f0-b1a6-e0bdb800fa7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019fc751-b535-79f0-b1a6-e0bdb800fa7a_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019fc751-b535-79f0-b1a6-e0bdb800fa7a" xlink:to="loc_dei_EntityDomain_019fc751-b535-79f0-b1a6-e0bdb800fa7a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019fc751-b535-7c08-b4b2-b8c5fb044bd9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019fc751-b535-79f0-b1a6-e0bdb800fa7a" xlink:to="loc_dei_EntityDomain_019fc751-b535-7c08-b4b2-b8c5fb044bd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_WoodStarReciprocalExchangeMember_019fc751-b535-7c2c-9688-1f332a27c09a" xlink:href="arx-20260630.xsd#arx_WoodStarReciprocalExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019fc751-b535-7c08-b4b2-b8c5fb044bd9" xlink:to="loc_arx_WoodStarReciprocalExchangeMember_019fc751-b535-7c2c-9688-1f332a27c09a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fc751-b535-7cd9-9281-b460e8878894" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fc751-b535-749c-8801-72bbc7609b0e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fc751-b535-7cd9-9281-b460e8878894" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fc751-b535-7cd9-9281-b460e8878894_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fc751-b535-7cd9-9281-b460e8878894" xlink:to="loc_us-gaap_RelatedPartyDomain_019fc751-b535-7cd9-9281-b460e8878894_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fc751-b535-709d-aa6a-7a2f6c2c68f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fc751-b535-7cd9-9281-b460e8878894" xlink:to="loc_us-gaap_RelatedPartyDomain_019fc751-b535-709d-aa6a-7a2f6c2c68f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_019fd7ba-442a-7f56-8f9b-59f358f33b5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fc751-b535-709d-aa6a-7a2f6c2c68f5" xlink:to="loc_us-gaap_NonrelatedPartyMember_019fd7ba-442a-7f56-8f9b-59f358f33b5e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019fd7ba-9646-75a7-8d3a-7db5097a04df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fc751-b535-709d-aa6a-7a2f6c2c68f5" xlink:to="loc_us-gaap_RelatedPartyMember_019fd7ba-9646-75a7-8d3a-7db5097a04df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019fd7bd-1c64-7025-822f-1391fa04c171" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fc751-b535-749c-8801-72bbc7609b0e" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019fd7bd-1c64-7025-822f-1391fa04c171" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019fd7bd-1c64-7025-822f-1391fa04c171_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019fd7bd-1c64-7025-822f-1391fa04c171" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019fd7bd-1c64-7025-822f-1391fa04c171_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019fd7bd-1c64-7369-a332-832d89b4c050" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019fd7bd-1c64-7025-822f-1391fa04c171" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019fd7bd-1c64-7369-a332-832d89b4c050" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_WoodStarReciprocalExchangeMember_019fd7bd-81d9-776d-97bc-dab0bbe25782" xlink:href="arx-20260630.xsd#arx_WoodStarReciprocalExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019fd7bd-1c64-7369-a332-832d89b4c050" xlink:to="loc_arx_WoodStarReciprocalExchangeMember_019fd7bd-81d9-776d-97bc-dab0bbe25782" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019fd7bb-5e0f-786f-83be-da7b94496aaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fc751-b535-704a-9376-3347a37b9f3e" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019fd7bb-5e0f-786f-83be-da7b94496aaa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_PaidInKindInterestUsedToFundInvestment_019fec31-f175-769d-ba77-3d2789929000" xlink:href="arx-20260630.xsd#arx_PaidInKindInterestUsedToFundInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fc751-b535-704a-9376-3347a37b9f3e" xlink:to="loc_arx_PaidInKindInterestUsedToFundInvestment_019fec31-f175-769d-ba77-3d2789929000" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_EquityMethodInvestmentMaximumExposureToLoss_019fe97d-4b3d-7119-87a8-2fc4e64a1677" xlink:href="arx-20260630.xsd#arx_EquityMethodInvestmentMaximumExposureToLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fc751-b535-704a-9376-3347a37b9f3e" xlink:to="loc_arx_EquityMethodInvestmentMaximumExposureToLoss_019fe97d-4b3d-7119-87a8-2fc4e64a1677" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SegmentinformationNarrativeDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SegmentinformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SegmentinformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-75d9-8bb2-f24d33f82a36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7ed3-b193-a0896c4b9971" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-75d9-8bb2-f24d33f82a36" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7ed3-b193-a0896c4b9971" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7006-9c24-d77f3966c1da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7ed3-b193-a0896c4b9971" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7006-9c24-d77f3966c1da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4af3-d2a0-7006-9c24-d77f3966c1da_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7006-9c24-d77f3966c1da" xlink:to="loc_us-gaap_SegmentDomain_019e4af3-d2a0-7006-9c24-d77f3966c1da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4af3-d2a0-726e-bd4c-2784ed185bc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7006-9c24-d77f3966c1da" xlink:to="loc_us-gaap_SegmentDomain_019e4af3-d2a0-726e-bd4c-2784ed185bc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MGAOperationsSegmentMember_019e4af3-d2a0-7e3a-a06f-4dc19475d06b" xlink:href="arx-20260630.xsd#arx_MGAOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-726e-bd4c-2784ed185bc2" xlink:to="loc_arx_MGAOperationsSegmentMember_019e4af3-d2a0-7e3a-a06f-4dc19475d06b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-79ba-8fd2-42847ba0781d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7ed3-b193-a0896c4b9971" xlink:to="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-79ba-8fd2-42847ba0781d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-79ba-8fd2-42847ba0781d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-79ba-8fd2-42847ba0781d" xlink:to="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-79ba-8fd2-42847ba0781d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7e5d-9400-7bb36f3ff047" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-79ba-8fd2-42847ba0781d" xlink:to="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7e5d-9400-7bb36f3ff047" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e4af3-d2a0-70f5-9d31-4fec49bd2f42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7e5d-9400-7bb36f3ff047" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e4af3-d2a0-70f5-9d31-4fec49bd2f42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019e4af3-d2a0-7bcc-8ba3-960f9bd1bc25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7e5d-9400-7bb36f3ff047" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019e4af3-d2a0-7bcc-8ba3-960f9bd1bc25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_019e4af3-d2a0-7889-b215-f070629e536d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-75d9-8bb2-f24d33f82a36" xlink:to="loc_us-gaap_NumberOfReportableSegments_019e4af3-d2a0-7889-b215-f070629e536d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019e4af3-d2a0-79f2-a979-ad25d098bc48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-75d9-8bb2-f24d33f82a36" xlink:to="loc_us-gaap_EquityMethodInvestments_019e4af3-d2a0-79f2-a979-ad25d098bc48" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SegmentinformationScheduleofSegmentReportingInformationDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SegmentinformationScheduleofSegmentReportingInformationDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SegmentinformationScheduleofSegmentReportingInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7205-8524-7666a93a8342" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7205-8524-7666a93a8342" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-72ac-85f5-85f7cd76e75b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7205-8524-7666a93a8342" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-72ac-85f5-85f7cd76e75b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4af3-d2a0-72ac-85f5-85f7cd76e75b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-72ac-85f5-85f7cd76e75b" xlink:to="loc_us-gaap_SegmentDomain_019e4af3-d2a0-72ac-85f5-85f7cd76e75b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4af3-d2a0-75bd-b89f-68773abb3288" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-72ac-85f5-85f7cd76e75b" xlink:to="loc_us-gaap_SegmentDomain_019e4af3-d2a0-75bd-b89f-68773abb3288" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ExchangeServicesSegmentMember_019e4af3-d2a0-7a6a-95fc-c8ad383c4725" xlink:href="arx-20260630.xsd#arx_ExchangeServicesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-75bd-b89f-68773abb3288" xlink:to="loc_arx_ExchangeServicesSegmentMember_019e4af3-d2a0-7a6a-95fc-c8ad383c4725" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MGAOperationsSegmentMember_019e4af3-d2a0-760a-8e8f-7def3a22b995" xlink:href="arx-20260630.xsd#arx_MGAOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-75bd-b89f-68773abb3288" xlink:to="loc_arx_MGAOperationsSegmentMember_019e4af3-d2a0-760a-8e8f-7def3a22b995" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_UnderwritingSegmentMember_019e4af3-d2a0-7133-905d-e0422db9f9b4" xlink:href="arx-20260630.xsd#arx_UnderwritingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-75bd-b89f-68773abb3288" xlink:to="loc_arx_UnderwritingSegmentMember_019e4af3-d2a0-7133-905d-e0422db9f9b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7bf6-934d-d5e0591b02d8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7205-8524-7666a93a8342" xlink:to="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7bf6-934d-d5e0591b02d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7bf6-934d-d5e0591b02d8_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7bf6-934d-d5e0591b02d8" xlink:to="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7bf6-934d-d5e0591b02d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-765b-ab8a-135f5cd47555" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7bf6-934d-d5e0591b02d8" xlink:to="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-765b-ab8a-135f5cd47555" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e4af3-d2a0-713a-aa96-7208a1ad63fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-765b-ab8a-135f5cd47555" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e4af3-d2a0-713a-aa96-7208a1ad63fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019e4af3-d2a0-7dd2-9e18-728d18141da6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-765b-ab8a-135f5cd47555" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019e4af3-d2a0-7dd2-9e18-728d18141da6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_019e4af3-d2a0-7100-86d8-2e1e969e638c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-765b-ab8a-135f5cd47555" xlink:to="loc_us-gaap_IntersegmentEliminationMember_019e4af3-d2a0-7100-86d8-2e1e969e638c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d2a0-772c-9f94-dc1f740067c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7205-8524-7666a93a8342" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d2a0-772c-9f94-dc1f740067c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4af3-d2a0-772c-9f94-dc1f740067c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d2a0-772c-9f94-dc1f740067c0" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4af3-d2a0-772c-9f94-dc1f740067c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4af3-d2a0-7a35-800b-a040a399cd3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d2a0-772c-9f94-dc1f740067c0" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4af3-d2a0-7a35-800b-a040a399cd3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4af3-d2a0-71a3-b252-7b466b494913" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4af3-d2a0-7a35-800b-a040a399cd3e" xlink:to="loc_us-gaap_RelatedPartyMember_019e4af3-d2a0-71a3-b252-7b466b494913" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_019e4af3-d2a0-7a05-b58f-8413222319a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4af3-d2a0-7a35-800b-a040a399cd3e" xlink:to="loc_us-gaap_NonrelatedPartyMember_019e4af3-d2a0-7a05-b58f-8413222319a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4af3-d2a0-7573-b4d1-3b5c519e71f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7205-8524-7666a93a8342" xlink:to="loc_us-gaap_AwardTypeAxis_019e4af3-d2a0-7573-b4d1-3b5c519e71f2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d2a0-7573-b4d1-3b5c519e71f2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d2a0-7573-b4d1-3b5c519e71f2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d2a0-7573-b4d1-3b5c519e71f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d2a0-7cdf-a842-226a344aa712" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d2a0-7573-b4d1-3b5c519e71f2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d2a0-7cdf-a842-226a344aa712" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ProfitsInterestAwardMember_019e4af3-d2a0-7710-8ea7-fcd0172e3271" xlink:href="arx-20260630.xsd#arx_ProfitsInterestAwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d2a0-7cdf-a842-226a344aa712" xlink:to="loc_arx_ProfitsInterestAwardMember_019e4af3-d2a0-7710-8ea7-fcd0172e3271" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_CededCommissionIncome_019e4af3-d2a0-7888-b7db-09c11639f261" xlink:href="arx-20260630.xsd#arx_CededCommissionIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_CededCommissionIncome_019e4af3-d2a0-7888-b7db-09c11639f261" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_DirectCommissionIncome_019e4af3-d2a0-74d9-afd8-2571157d6e9a" xlink:href="arx-20260630.xsd#arx_DirectCommissionIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_DirectCommissionIncome_019e4af3-d2a0-74d9-afd8-2571157d6e9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsEarnedNet_019e4af3-d2a0-7d6b-ad13-42573a5d39f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsEarnedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_PremiumsEarnedNet_019e4af3-d2a0-7d6b-ad13-42573a5d39f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019e4af3-d2a0-758e-9506-81b6d020eae7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_NetInvestmentIncome_019e4af3-d2a0-758e-9506-81b6d020eae7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_OperatingRevenues_019e4af3-d2a0-717c-af3e-eab8dbce249c" xlink:href="arx-20260630.xsd#arx_OperatingRevenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_OperatingRevenues_019e4af3-d2a0-717c-af3e-eab8dbce249c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019e4af3-d2a0-76a9-8186-8f8912bf653e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PolicyholderBenefitsAndClaimsIncurredNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_PolicyholderBenefitsAndClaimsIncurredNet_019e4af3-d2a0-76a9-8186-8f8912bf653e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_019e4af3-d2a0-7267-9710-4a5d172e4942" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense_019e4af3-d2a0-7267-9710-4a5d172e4942" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_GeneralAndAdministrationExpenseExcludingShareBasedCompensation_019e4af3-d2a0-7839-bb7a-e1447cce01e7" xlink:href="arx-20260630.xsd#arx_GeneralAndAdministrationExpenseExcludingShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_GeneralAndAdministrationExpenseExcludingShareBasedCompensation_019e4af3-d2a0-7839-bb7a-e1447cce01e7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_019e4af3-d2a0-7d18-a947-0826e856f174" xlink:href="arx-20260630.xsd#arx_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_019e4af3-d2a0-7d18-a947-0826e856f174" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedInvestmentGainsLosses_019e4af3-d2a0-74f0-9f50-176af160a4ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealizedInvestmentGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_RealizedInvestmentGainsLosses_019e4af3-d2a0-74f0-9f50-176af160a4ae" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019e4af3-d2a0-778b-8166-86a05bf9bdaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019e4af3-d2a0-778b-8166-86a05bf9bdaf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4af3-d2a0-7218-b8b1-2288cb97ae65" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4af3-d2a0-7218-b8b1-2288cb97ae65" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019e4af3-d2a0-735b-b906-1ff1712415c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_InterestExpenseDebt_019e4af3-d2a0-735b-b906-1ff1712415c3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019e4af3-d2a0-7754-ad61-ca496160f15e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_DepreciationAndAmortization_019e4af3-d2a0-7754-ad61-ca496160f15e" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019e4af3-d2a0-772d-a07d-62dc30f259e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_019e4af3-d2a0-772d-a07d-62dc30f259e3" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingExpense_019e4af3-d2a0-7c64-bf93-0b46ca2b5ccd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_OtherNonoperatingExpense_019e4af3-d2a0-7c64-bf93-0b46ca2b5ccd" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e4af3-d2a0-7b13-a7a4-462788285f18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e4af3-d2a0-7b13-a7a4-462788285f18" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019e4af3-d2a0-70b5-8366-cccbf52a6213" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019e4af3-d2a0-70b5-8366-cccbf52a6213" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019e4af3-d2a0-7dbf-8f96-c2009a5a5399" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_ProfessionalFees_019e4af3-d2a0-7dbf-8f96-c2009a5a5399" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019e4af3-d2a0-78f2-a42e-e8c6e6cde4bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_OtherGeneralAndAdministrativeExpense_019e4af3-d2a0-78f2-a42e-e8c6e6cde4bd" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019e4af3-d2a0-7c95-8d71-ba4bd885a4c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019e4af3-d2a0-7c95-8d71-ba4bd885a4c7" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_CorporateDevelopmentAndCapitalRiseExpense_019e4af3-d2a0-7934-9f2e-b4fbdfdf72fc" xlink:href="arx-20260630.xsd#arx_CorporateDevelopmentAndCapitalRiseExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_CorporateDevelopmentAndCapitalRiseExpense_019e4af3-d2a0-7934-9f2e-b4fbdfdf72fc" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_SystemDevelopmentExpenseNonOperating_019e4af3-d2a0-776b-b990-23ba60d1009c" xlink:href="arx-20260630.xsd#arx_SystemDevelopmentExpenseNonOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_SystemDevelopmentExpenseNonOperating_019e4af3-d2a0-776b-b990-23ba60d1009c" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ProfitSharingExpense_019e4af3-d2a0-7e96-b6e0-6c25f6bb01d1" xlink:href="arx-20260630.xsd#arx_ProfitSharingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_ProfitSharingExpense_019e4af3-d2a0-7e96-b6e0-6c25f6bb01d1" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ProfitSharingExpenseBuyOut_019fda4e-5140-79ca-8e8d-47270d53e57d" xlink:href="arx-20260630.xsd#arx_ProfitSharingExpenseBuyOut"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_ProfitSharingExpenseBuyOut_019fda4e-5140-79ca-8e8d-47270d53e57d" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MiscellaneousExpenses_019e4af3-d2a0-7ab6-bf02-8fe95971795f" xlink:href="arx-20260630.xsd#arx_MiscellaneousExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-762c-bf0d-0542dfd57f66" xlink:to="loc_arx_MiscellaneousExpenses_019e4af3-d2a0-7ab6-bf02-8fe95971795f" xlink:type="arc" order="25"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SegmentinformationScheduleofAssetsbySegmentDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SegmentinformationScheduleofAssetsbySegmentDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SegmentinformationScheduleofAssetsbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7b71-b4ff-9c68317ab861" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7d7b-b745-953385407456" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7b71-b4ff-9c68317ab861" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7d7b-b745-953385407456" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7cfe-98b2-52d01b0e63b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7d7b-b745-953385407456" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7cfe-98b2-52d01b0e63b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4af3-d2a0-7cfe-98b2-52d01b0e63b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7cfe-98b2-52d01b0e63b4" xlink:to="loc_us-gaap_SegmentDomain_019e4af3-d2a0-7cfe-98b2-52d01b0e63b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4af3-d2a0-71dd-b393-429f5f808b1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4af3-d2a0-7cfe-98b2-52d01b0e63b4" xlink:to="loc_us-gaap_SegmentDomain_019e4af3-d2a0-71dd-b393-429f5f808b1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ExchangeServicesSegmentMember_019e4af3-d2a0-7684-b751-dd69d071f33c" xlink:href="arx-20260630.xsd#arx_ExchangeServicesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-71dd-b393-429f5f808b1a" xlink:to="loc_arx_ExchangeServicesSegmentMember_019e4af3-d2a0-7684-b751-dd69d071f33c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MGAOperationsSegmentMember_019e4af3-d2a0-78e4-a77d-0bca415466e2" xlink:href="arx-20260630.xsd#arx_MGAOperationsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-71dd-b393-429f5f808b1a" xlink:to="loc_arx_MGAOperationsSegmentMember_019e4af3-d2a0-78e4-a77d-0bca415466e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_UnderwritingSegmentMember_019e4af3-d2a0-761f-b8ca-7ebdcd4675e2" xlink:href="arx-20260630.xsd#arx_UnderwritingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4af3-d2a0-71dd-b393-429f5f808b1a" xlink:to="loc_arx_UnderwritingSegmentMember_019e4af3-d2a0-761f-b8ca-7ebdcd4675e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7211-943c-04482220b908" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7d7b-b745-953385407456" xlink:to="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7211-943c-04482220b908" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7211-943c-04482220b908_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7211-943c-04482220b908" xlink:to="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-7211-943c-04482220b908_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-760a-b476-6d77c821ecae" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e4af3-d2a0-7211-943c-04482220b908" xlink:to="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-760a-b476-6d77c821ecae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e4af3-d2a0-784e-8818-378d25b9653d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-760a-b476-6d77c821ecae" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e4af3-d2a0-784e-8818-378d25b9653d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_CorporateAndEliminationsMember_019e4af3-d2a0-7db3-aef9-e719b187d5ff" xlink:href="arx-20260630.xsd#arx_CorporateAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e4af3-d2a0-760a-b476-6d77c821ecae" xlink:to="loc_arx_CorporateAndEliminationsMember_019e4af3-d2a0-7db3-aef9-e719b187d5ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e4af3-d2a0-750f-84c8-e88f10730ca7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7b71-b4ff-9c68317ab861" xlink:to="loc_us-gaap_Assets_019e4af3-d2a0-750f-84c8-e88f10730ca7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SegmentinformationScheduleofRevenuesbyGeographyDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SegmentinformationScheduleofRevenuesbyGeographyDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SegmentinformationScheduleofRevenuesbyGeographyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7bae-aac3-6e5131b5a2d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7bae-aac3-6e5131b5a2d7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019e4af3-d2a0-7291-9df8-076f50cd75e4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e4af3-d2a0-7bae-aac3-6e5131b5a2d7" xlink:to="loc_srt_StatementGeographicalAxis_019e4af3-d2a0-7291-9df8-076f50cd75e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e4af3-d2a0-7291-9df8-076f50cd75e4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019e4af3-d2a0-7291-9df8-076f50cd75e4" xlink:to="loc_srt_SegmentGeographicalDomain_019e4af3-d2a0-7291-9df8-076f50cd75e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e4af3-d2a0-729e-a45d-da3e29667d73" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019e4af3-d2a0-7291-9df8-076f50cd75e4" xlink:to="loc_srt_SegmentGeographicalDomain_019e4af3-d2a0-729e-a45d-da3e29667d73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NorthAmericaMember_019e4af3-d2a0-70d5-b5b9-95fdb404e833" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NorthAmericaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4af3-d2a0-729e-a45d-da3e29667d73" xlink:to="loc_srt_NorthAmericaMember_019e4af3-d2a0-70d5-b5b9-95fdb404e833" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_UnitedKingdomAndEuropeanUnionMember_019e4af3-d2a0-7553-b4d6-7845a6fd4a2e" xlink:href="arx-20260630.xsd#arx_UnitedKingdomAndEuropeanUnionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4af3-d2a0-729e-a45d-da3e29667d73" xlink:to="loc_arx_UnitedKingdomAndEuropeanUnionMember_019e4af3-d2a0-7553-b4d6-7845a6fd4a2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_CededCommissionIncome_019e4af3-d2a0-77c1-8ab2-fc7816441e2c" xlink:href="arx-20260630.xsd#arx_CededCommissionIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_arx_CededCommissionIncome_019e4af3-d2a0-77c1-8ab2-fc7816441e2c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_DirectCommissionIncome_019e4af3-d2a0-7a23-a1dc-de185e724f80" xlink:href="arx-20260630.xsd#arx_DirectCommissionIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_arx_DirectCommissionIncome_019e4af3-d2a0-7a23-a1dc-de185e724f80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsEarnedNet_019e4af3-d2a0-7b1a-abf6-c094e2589e97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsEarnedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_us-gaap_PremiumsEarnedNet_019e4af3-d2a0-7b1a-abf6-c094e2589e97" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019e4af3-d2a0-71cb-acfd-c8c577a9a65d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_us-gaap_NetInvestmentIncome_019e4af3-d2a0-71cb-acfd-c8c577a9a65d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealizedInvestmentGainsLosses_019e4af3-d2a0-7332-b484-d72db702a077" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealizedInvestmentGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_us-gaap_RealizedInvestmentGainsLosses_019e4af3-d2a0-7332-b484-d72db702a077" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019e4af3-d2a0-7794-9d56-39ba52a92dfd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019e4af3-d2a0-7794-9d56-39ba52a92dfd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4af3-d2a0-70fc-b41d-5c19d58733e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e4af3-d2a0-7dba-8886-3df3c05dc16b" xlink:to="loc_us-gaap_Revenues_019e4af3-d2a0-70fc-b41d-5c19d58733e3" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofUnrealizedGainsandLossesonAvailableforSaleFixedMaturityandShortTermInvestmentsatFairValueDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofUnrealizedGainsandLossesonAvailableforSaleFixedMaturityandShortTermInvestmentsatFairValueDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofUnrealizedGainsandLossesonAvailableforSaleFixedMaturityandShortTermInvestmentsatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7f67-b46e-a839a8d6b83c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-7ad3-b08b-ffd14e43915b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7f67-b46e-a839a8d6b83c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-7ad3-b08b-ffd14e43915b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-71ec-9a93-8ca1ec6f61c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-7ad3-b08b-ffd14e43915b" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-71ec-9a93-8ca1ec6f61c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-71ec-9a93-8ca1ec6f61c0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-71ec-9a93-8ca1ec6f61c0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-71ec-9a93-8ca1ec6f61c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-71ec-9a93-8ca1ec6f61c0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019e4af3-d2a0-7a78-a0ca-7ceeeb90a113" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019e4af3-d2a0-7a78-a0ca-7ceeeb90a113" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019e4af3-d2a0-72c9-bfca-a78d3aca8c3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019e4af3-d2a0-72c9-bfca-a78d3aca8c3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019e4af3-d2a0-77d6-88e6-605f1b0e2c3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019e4af3-d2a0-77d6-88e6-605f1b0e2c3d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-7ebc-b919-343897d552d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-7ebc-b919-343897d552d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019e4af3-d2a0-704a-8bc3-efbe8308f186" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019e4af3-d2a0-704a-8bc3-efbe8308f186" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_OtherAssetBackedSecuritiesMember_019e4af3-d2a0-7b1f-9974-8e84124e0f67" xlink:href="arx-20260630.xsd#arx_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e1b-8a60-392d02da5529" xlink:to="loc_arx_OtherAssetBackedSecuritiesMember_019e4af3-d2a0-7b1f-9974-8e84124e0f67" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e4af3-d2a0-77c6-b83a-70d400a5c579" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7f67-b46e-a839a8d6b83c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e4af3-d2a0-77c6-b83a-70d400a5c579" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019e4af3-d2a0-7a91-837c-a087dd7456cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7f67-b46e-a839a8d6b83c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019e4af3-d2a0-7a91-837c-a087dd7456cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019e4af3-d2a0-794a-8a20-ec2fc46eb73f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7f67-b46e-a839a8d6b83c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019e4af3-d2a0-794a-8a20-ec2fc46eb73f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d2a0-7167-b3b6-ad0c721a2289" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7f67-b46e-a839a8d6b83c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d2a0-7167-b3b6-ad0c721a2289" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofContinuousLossPositionDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofContinuousLossPositionDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofContinuousLossPositionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7d43-a2d3-79719e764e67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-78e8-9108-ed1bcda956dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7d43-a2d3-79719e764e67" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-78e8-9108-ed1bcda956dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-79d7-a1a4-80ee7934f63e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-78e8-9108-ed1bcda956dc" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-79d7-a1a4-80ee7934f63e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-79d7-a1a4-80ee7934f63e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-79d7-a1a4-80ee7934f63e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-79d7-a1a4-80ee7934f63e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-79d7-a1a4-80ee7934f63e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019e4af3-d2a0-7acf-b57a-734131776927" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019e4af3-d2a0-7acf-b57a-734131776927" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019e4af3-d2a0-7e9d-aea7-bd37f267e9db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019e4af3-d2a0-7e9d-aea7-bd37f267e9db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019e4af3-d2a0-7af2-8da5-cce4c787d2a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019e4af3-d2a0-7af2-8da5-cce4c787d2a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-775e-b980-7356b3d51e6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-775e-b980-7356b3d51e6d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_OtherAssetBackedSecuritiesMember_019fa76c-9938-7a82-abe5-1a901c8536d3" xlink:href="arx-20260630.xsd#arx_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-779a-8698-824e3fb93955" xlink:to="loc_arx_OtherAssetBackedSecuritiesMember_019fa76c-9938-7a82-abe5-1a901c8536d3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019e4af3-d2a0-71b3-aa3b-7391d58c46f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7d43-a2d3-79719e764e67" xlink:to="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019e4af3-d2a0-71b3-aa3b-7391d58c46f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019e4af3-d2a0-7c5e-ab37-4cf5f67bbb5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019e4af3-d2a0-71b3-aa3b-7391d58c46f4" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019e4af3-d2a0-7c5e-ab37-4cf5f67bbb5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019e4af3-d2a0-723a-8f0e-7574e343c1a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019e4af3-d2a0-71b3-aa3b-7391d58c46f4" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019e4af3-d2a0-723a-8f0e-7574e343c1a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019e4af3-d2a0-7cdf-bcde-cb8e17d85cba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAvailableforSaleUnrealizedLossPositionAbstract_019e4af3-d2a0-71b3-aa3b-7391d58c46f4" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019e4af3-d2a0-7cdf-bcde-cb8e17d85cba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019e4af3-d2a0-75ce-bc49-b751691c8708" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-7d43-a2d3-79719e764e67" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019e4af3-d2a0-75ce-bc49-b751691c8708" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019e4af3-d2a0-7791-81fa-2a4ce1b6c333" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019e4af3-d2a0-75ce-bc49-b751691c8708" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019e4af3-d2a0-7791-81fa-2a4ce1b6c333" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019e4af3-d2a0-71bb-9a69-de76b29281b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019e4af3-d2a0-75ce-bc49-b751691c8708" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019e4af3-d2a0-71bb-9a69-de76b29281b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019e4af3-d2a0-751b-bd21-9092a288d8f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_019e4af3-d2a0-75ce-bc49-b751691c8708" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019e4af3-d2a0-751b-bd21-9092a288d8f8" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofFixedmaturitySecuritiesClassifiedbyContractualMaturitySecuritiesDateDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofFixedmaturitySecuritiesClassifiedbyContractualMaturitySecuritiesDateDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofFixedmaturitySecuritiesClassifiedbyContractualMaturitySecuritiesDateDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-70f7-bd14-a11e02929b49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-740d-9a49-02ab90782225" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-70f7-bd14-a11e02929b49" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-740d-9a49-02ab90782225" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7c2e-8275-876b4bc0ced4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e4af3-d2a0-740d-9a49-02ab90782225" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7c2e-8275-876b4bc0ced4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7c2e-8275-876b4bc0ced4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7c2e-8275-876b4bc0ced4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7c2e-8275-876b4bc0ced4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7da3-99ef-d2f8b445698f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7c2e-8275-876b4bc0ced4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7da3-99ef-d2f8b445698f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-723d-ad67-8162b2ca8f11" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7da3-99ef-d2f8b445698f" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-723d-ad67-8162b2ca8f11" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019e4af3-d2a0-7031-ab07-603409a6d3a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7da3-99ef-d2f8b445698f" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019e4af3-d2a0-7031-ab07-603409a6d3a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_OtherAssetBackedSecuritiesMember_019e4af3-d2a0-75cf-b366-faef826ddf94" xlink:href="arx-20260630.xsd#arx_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7da3-99ef-d2f8b445698f" xlink:to="loc_arx_OtherAssetBackedSecuritiesMember_019e4af3-d2a0-75cf-b366-faef826ddf94" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-70f7-bd14-a11e02929b49" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_019e4af3-d2a0-7f72-9561-a218c7adcd46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_019e4af3-d2a0-7f72-9561-a218c7adcd46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_019e4af3-d2a0-7df4-bee9-b80611b7352a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_019e4af3-d2a0-7df4-bee9-b80611b7352a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_019e4af3-d2a0-79c4-9599-2e6455fb5d29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost_019e4af3-d2a0-79c4-9599-2e6455fb5d29" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_019e4af3-d2a0-73cd-88b7-f810a3ccf0ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_019e4af3-d2a0-73cd-88b7-f810a3ccf0ed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost_019e4af3-d2a0-7dce-87b2-b021a53b8f92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost_019e4af3-d2a0-7dce-87b2-b021a53b8f92" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e4af3-d2a0-7a43-83ce-ad68127abac0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_019e4af3-d2a0-7b3c-ad46-5de2a16b6c3c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019e4af3-d2a0-7a43-83ce-ad68127abac0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e4af3-d2a0-70f7-bd14-a11e02929b49" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_019e4af3-d2a0-798d-ac16-237f6c4897c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_019e4af3-d2a0-798d-ac16-237f6c4897c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_019e4af3-d2a0-7e86-9e8b-c6f41ad7aee0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_019e4af3-d2a0-7e86-9e8b-c6f41ad7aee0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_019e4af3-d2a0-77fc-9f0e-83d754302b23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue_019e4af3-d2a0-77fc-9f0e-83d754302b23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_019e4af3-d2a0-713b-ad7c-fb1ea0b4dad1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_019e4af3-d2a0-713b-ad7c-fb1ea0b4dad1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue_019e4af3-d2a0-78b6-be15-b3d4e9d600b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue_019e4af3-d2a0-78b6-be15-b3d4e9d600b3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d2a0-7ec9-8e06-e7b61569f5d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_019e4af3-d2a0-7d49-af72-e321721a2ba9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d2a0-7ec9-8e06-e7b61569f5d1" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofEquityMethodInvestmentsDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofEquityMethodInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofEquityMethodInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7b2b-90ec-d221b0b32622" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-793f-8184-44fc4635fb17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7b2b-90ec-d221b0b32622" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-793f-8184-44fc4635fb17" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4af3-d2a0-7534-8b26-c23efdafb161" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-793f-8184-44fc4635fb17" xlink:to="loc_srt_RangeAxis_019e4af3-d2a0-7534-8b26-c23efdafb161" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4af3-d2a0-7534-8b26-c23efdafb161_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4af3-d2a0-7534-8b26-c23efdafb161" xlink:to="loc_srt_RangeMember_019e4af3-d2a0-7534-8b26-c23efdafb161_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4af3-d2a0-7db6-8700-d8a030ef2aff" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4af3-d2a0-7534-8b26-c23efdafb161" xlink:to="loc_srt_RangeMember_019e4af3-d2a0-7db6-8700-d8a030ef2aff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4af3-d2a0-7b20-a7f9-52ebb0376dd4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4af3-d2a0-7db6-8700-d8a030ef2aff" xlink:to="loc_srt_MinimumMember_019e4af3-d2a0-7b20-a7f9-52ebb0376dd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4af3-d2a0-726a-8019-96694e0ea30c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4af3-d2a0-7db6-8700-d8a030ef2aff" xlink:to="loc_srt_MaximumMember_019e4af3-d2a0-726a-8019-96694e0ea30c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e4af3-d2a0-77d3-afc7-265aeb8ac966" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-793f-8184-44fc4635fb17" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e4af3-d2a0-77d3-afc7-265aeb8ac966" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019e4af3-d2a0-77d3-afc7-265aeb8ac966_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e4af3-d2a0-77d3-afc7-265aeb8ac966" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019e4af3-d2a0-77d3-afc7-265aeb8ac966_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019e4af3-d2a0-7397-8c3a-a7ec963be8ef" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019e4af3-d2a0-77d3-afc7-265aeb8ac966" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019e4af3-d2a0-7397-8c3a-a7ec963be8ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ManagingGeneralAgentsMember_019e4af3-d2a0-7a02-8cef-00ed9c7e91f8" xlink:href="arx-20260630.xsd#arx_ManagingGeneralAgentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e4af3-d2a0-7397-8c3a-a7ec963be8ef" xlink:to="loc_arx_ManagingGeneralAgentsMember_019e4af3-d2a0-7a02-8cef-00ed9c7e91f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_OtherMember_019e4af3-d2a0-741d-a05d-89621386c843" xlink:href="arx-20260630.xsd#arx_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019e4af3-d2a0-7397-8c3a-a7ec963be8ef" xlink:to="loc_arx_OtherMember_019e4af3-d2a0-741d-a05d-89621386c843" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019e4af3-d2a0-7d95-9896-db27598cf2ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7b2b-90ec-d221b0b32622" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019e4af3-d2a0-7d95-9896-db27598cf2ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019e4af3-d2a0-7418-b3aa-ec217a4036b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7b2b-90ec-d221b0b32622" xlink:to="loc_us-gaap_EquityMethodInvestments_019e4af3-d2a0-7418-b3aa-ec217a4036b8" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsNarrativeDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7d83-925e-a6fffc3aa443" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7d83-925e-a6fffc3aa443" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7784-be9f-18798337b0cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7d83-925e-a6fffc3aa443" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7784-be9f-18798337b0cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7784-be9f-18798337b0cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7784-be9f-18798337b0cd" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7784-be9f-18798337b0cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-720d-b6d5-89f74ad1a06d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7784-be9f-18798337b0cd" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-720d-b6d5-89f74ad1a06d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_VentureFundsMember_019e4af3-d2a0-70da-993a-e113a45cfe0f" xlink:href="arx-20260630.xsd#arx_VentureFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-720d-b6d5-89f74ad1a06d" xlink:to="loc_arx_VentureFundsMember_019e4af3-d2a0-70da-993a-e113a45cfe0f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_EquityMethodInvestmentsUnfundedCommitments_019e4af3-d2a0-7761-8ba4-937f20d83d8a" xlink:href="arx-20260630.xsd#arx_EquityMethodInvestmentsUnfundedCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_arx_EquityMethodInvestmentsUnfundedCommitments_019e4af3-d2a0-7761-8ba4-937f20d83d8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_019e4af3-d2a0-70b2-8a4f-c649510ef0ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentDividendsOrDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_019e4af3-d2a0-70b2-8a4f-c649510ef0ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019fd5e0-7b7a-7927-a392-d7f1d45fd95d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019fd5e0-7b7a-7927-a392-d7f1d45fd95d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_EquitySecuritiesSoldReamingInvestment_019fd7f2-eeb9-7e0c-968f-290ef430e552" xlink:href="arx-20260630.xsd#arx_EquitySecuritiesSoldReamingInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_arx_EquitySecuritiesSoldReamingInvestment_019fd7f2-eeb9-7e0c-968f-290ef430e552" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019fd5e0-7b7a-7a3b-ac37-7dfc58a9dd31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019fd5e0-7b7a-7a3b-ac37-7dfc58a9dd31" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount_019e4af3-d2a0-7ee7-83ac-b0980730cb31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount_019e4af3-d2a0-7ee7-83ac-b0980730cb31" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_019e4af3-d2a0-78e3-9568-12afa04bc14c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_019e4af3-d2a0-78e3-9568-12afa04bc14c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount_019e4af3-d2a0-742a-8fce-aeed7795ccbd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount_019e4af3-d2a0-742a-8fce-aeed7795ccbd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount_019e4af3-d2a0-7483-a235-838a5f0a7436" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossCumulativeAmount_019e4af3-d2a0-7483-a235-838a5f0a7436" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_EquitySecuritiesWithoutReadilyDeterminableFairValueUnfundedCommitments_019e4af3-d2a0-7fa6-8c6f-f66197d0b047" xlink:href="arx-20260630.xsd#arx_EquitySecuritiesWithoutReadilyDeterminableFairValueUnfundedCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_arx_EquitySecuritiesWithoutReadilyDeterminableFairValueUnfundedCommitments_019e4af3-d2a0-7fa6-8c6f-f66197d0b047" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss_019fd7d2-c179-714c-8866-c4a398b2fc6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7c3a-a53d-de25b4ca6cb0" xlink:to="loc_us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss_019fd7d2-c179-714c-8866-c4a398b2fc6d" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofCarryingValueofOurOtherInvestmentsPortfolioDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofCarryingValueofOurOtherInvestmentsPortfolioDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofCarryingValueofOurOtherInvestmentsPortfolioDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7e0b-920f-f01b72f21758" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7d69-b889-e03566fb2d80" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7e0b-920f-f01b72f21758" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7d69-b889-e03566fb2d80" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-73e3-82ac-d4a69ee14292" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7d69-b889-e03566fb2d80" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-73e3-82ac-d4a69ee14292" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-73e3-82ac-d4a69ee14292_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-73e3-82ac-d4a69ee14292" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-73e3-82ac-d4a69ee14292_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7b7b-9341-ffc4b81135cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-73e3-82ac-d4a69ee14292" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7b7b-9341-ffc4b81135cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MGAsAndTPAsMember_019e4af3-d2a0-7aef-bca1-b3baabd4594c" xlink:href="arx-20260630.xsd#arx_MGAsAndTPAsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7b7b-9341-ffc4b81135cd" xlink:to="loc_arx_MGAsAndTPAsMember_019e4af3-d2a0-7aef-bca1-b3baabd4594c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_VentureFundsMember_019e4af3-d2a0-700c-97c3-5457401c01e7" xlink:href="arx-20260630.xsd#arx_VentureFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7b7b-9341-ffc4b81135cd" xlink:to="loc_arx_VentureFundsMember_019e4af3-d2a0-700c-97c3-5457401c01e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d2a0-7396-94e1-8175e7e355df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7e0b-920f-f01b72f21758" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d2a0-7396-94e1-8175e7e355df" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofInvestmentIncomeandExpensesDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofInvestmentIncomeandExpensesDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofInvestmentIncomeandExpensesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable_019e4af3-d2a0-7a2b-b300-62cfb0b6c682" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable_019e4af3-d2a0-7a2b-b300-62cfb0b6c682" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7891-8081-68a9aad413aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryTable_019e4af3-d2a0-7a2b-b300-62cfb0b6c682" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7891-8081-68a9aad413aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7891-8081-68a9aad413aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7891-8081-68a9aad413aa" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7891-8081-68a9aad413aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7ee0-83b3-c6a49a123b8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7891-8081-68a9aad413aa" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7ee0-83b3-c6a49a123b8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_019e4af3-d2a0-7738-9d1a-979c4f7e731a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7ee0-83b3-c6a49a123b8b" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_019e4af3-d2a0-7738-9d1a-979c4f7e731a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019e4af3-d2a0-73fd-a71d-7426a251e497" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7ee0-83b3-c6a49a123b8b" xlink:to="loc_us-gaap_FixedMaturitiesMember_019e4af3-d2a0-73fd-a71d-7426a251e497" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019e4af3-d2a0-7d46-a862-ac2d2bc27b36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019e4af3-d2a0-7d46-a862-ac2d2bc27b36" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019e4af3-d2a0-7567-a6c3-7d969949be3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019e4af3-d2a0-7567-a6c3-7d969949be3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossInvestmentIncomeOperating_019e4af3-d2a0-74fe-b632-eb8a8787f10c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossInvestmentIncomeOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_us-gaap_GrossInvestmentIncomeOperating_019e4af3-d2a0-74fe-b632-eb8a8787f10c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_InvestmentExpenseInterestOnFundsHeldUnderReinsurance_019e4af3-d2a0-72d2-a8ae-b7998cbdeba7" xlink:href="arx-20260630.xsd#arx_InvestmentExpenseInterestOnFundsHeldUnderReinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_arx_InvestmentExpenseInterestOnFundsHeldUnderReinsurance_019e4af3-d2a0-72d2-a8ae-b7998cbdeba7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e4af3-d2a0-7e53-9a09-d97d0d28d68c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIncomeInvestmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_us-gaap_InvestmentIncomeInvestmentExpense_019e4af3-d2a0-7e53-9a09-d97d0d28d68c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentIncome_019e4af3-d2a0-70e7-98a8-3d426e3da6db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetInvestmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentIncomeReportedAmountsByCategoryLineItems_019e4af3-d2a0-7cc6-8aca-1407a31caf52" xlink:to="loc_us-gaap_NetInvestmentIncome_019e4af3-d2a0-70e7-98a8-3d426e3da6db" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofDepositsforRegulatoryandOtherPurposesDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofDepositsforRegulatoryandOtherPurposesDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofDepositsforRegulatoryandOtherPurposesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7ddc-bbdb-2fefe4475315" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-71a6-91c9-4d39992237e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7ddc-bbdb-2fefe4475315" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-71a6-91c9-4d39992237e1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-717b-aa91-655c00ead3d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-71a6-91c9-4d39992237e1" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-717b-aa91-655c00ead3d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-717b-aa91-655c00ead3d0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-717b-aa91-655c00ead3d0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-717b-aa91-655c00ead3d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7398-97e2-b0cb3bbb8b35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-717b-aa91-655c00ead3d0" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7398-97e2-b0cb3bbb8b35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019e4af3-d2a0-7497-bebc-7cfd48c34c47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7398-97e2-b0cb3bbb8b35" xlink:to="loc_us-gaap_FixedMaturitiesMember_019e4af3-d2a0-7497-bebc-7cfd48c34c47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_019e4af3-d2a0-7976-abc5-1df42f3bd9af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7398-97e2-b0cb3bbb8b35" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_019e4af3-d2a0-7976-abc5-1df42f3bd9af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositAssets_019e4af3-d2a0-7a5f-92f0-ccc4342bc762" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepositAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-7ddc-bbdb-2fefe4475315" xlink:to="loc_us-gaap_DepositAssets_019e4af3-d2a0-7a5f-92f0-ccc4342bc762" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/InvestmentsScheduleofCollateralizedObligationsDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#InvestmentsScheduleofCollateralizedObligationsDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/InvestmentsScheduleofCollateralizedObligationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-77e0-b8e3-fd8107f50f2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7cde-84bf-cf2a283f7381" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-77e0-b8e3-fd8107f50f2e" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7cde-84bf-cf2a283f7381" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7e32-b9bf-5e7c8a8fe480" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7cde-84bf-cf2a283f7381" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7e32-b9bf-5e7c8a8fe480" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e32-b9bf-5e7c8a8fe480_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7e32-b9bf-5e7c8a8fe480" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7e32-b9bf-5e7c8a8fe480_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-79cc-a505-3a54f8a20079" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7e32-b9bf-5e7c8a8fe480" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-79cc-a505-3a54f8a20079" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_019e4af3-d2a0-7cb5-a637-e41b9c640075" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-79cc-a505-3a54f8a20079" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_019e4af3-d2a0-7cb5-a637-e41b9c640075" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedMaturitiesMember_019e4af3-d2a0-70f6-9f58-33b439295437" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FixedMaturitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-79cc-a505-3a54f8a20079" xlink:to="loc_us-gaap_FixedMaturitiesMember_019e4af3-d2a0-70f6-9f58-33b439295437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_019e4af3-d2a0-746d-a526-50c7031cee42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019e4af3-d2a0-7cde-84bf-cf2a283f7381" xlink:to="loc_us-gaap_PledgedStatusAxis_019e4af3-d2a0-746d-a526-50c7031cee42" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019e4af3-d2a0-746d-a526-50c7031cee42_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_019e4af3-d2a0-746d-a526-50c7031cee42" xlink:to="loc_us-gaap_PledgedStatusDomain_019e4af3-d2a0-746d-a526-50c7031cee42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_019e4af3-d2a0-72df-bf51-001482373612" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_019e4af3-d2a0-746d-a526-50c7031cee42" xlink:to="loc_us-gaap_PledgedStatusDomain_019e4af3-d2a0-72df-bf51-001482373612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralMember_019e4af3-d2a0-7f58-b9de-05a842d2fd27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetPledgedAsCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_019e4af3-d2a0-72df-bf51-001482373612" xlink:to="loc_us-gaap_AssetPledgedAsCollateralMember_019e4af3-d2a0-7f58-b9de-05a842d2fd27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedInvestments_019e4af3-d2a0-7051-a8c8-5bb5301ba110" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-77e0-b8e3-fd8107f50f2e" xlink:to="loc_us-gaap_RestrictedInvestments_019e4af3-d2a0-7051-a8c8-5bb5301ba110" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_019e4af3-d2a0-752b-bcbc-f22c55f8c10f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-77e0-b8e3-fd8107f50f2e" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_019e4af3-d2a0-752b-bcbc-f22c55f8c10f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndInvestments_019e4af3-d2a0-72c1-ad7e-f7d2a69bb998" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019e4af3-d2a0-77e0-b8e3-fd8107f50f2e" xlink:to="loc_us-gaap_RestrictedCashAndInvestments_019e4af3-d2a0-72c1-ad7e-f7d2a69bb998" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/FairvaluemeasurementsScheduleofFinancialAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisbyLevelDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#FairvaluemeasurementsScheduleofFinancialAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisbyLevelDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/FairvaluemeasurementsScheduleofFinancialAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisbyLevelDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4af3-d2a0-746d-adfb-3c14ddc734fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-7b1b-a9ab-6f633757665b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4af3-d2a0-746d-adfb-3c14ddc734fa" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-7b1b-a9ab-6f633757665b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-75b4-ac66-923999bc7d20" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-7b1b-a9ab-6f633757665b" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-75b4-ac66-923999bc7d20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-75b4-ac66-923999bc7d20_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-75b4-ac66-923999bc7d20" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-75b4-ac66-923999bc7d20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-79de-88c0-16abe61aa76e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-75b4-ac66-923999bc7d20" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-79de-88c0-16abe61aa76e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019e4af3-d2a0-7e6f-9ba9-b1dc930da33e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-79de-88c0-16abe61aa76e" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019e4af3-d2a0-7e6f-9ba9-b1dc930da33e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-7bb1-a99e-70dc56c788cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-7b1b-a9ab-6f633757665b" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-7bb1-a99e-70dc56c788cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7bb1-a99e-70dc56c788cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-7bb1-a99e-70dc56c788cc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7bb1-a99e-70dc56c788cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7354-b795-9f4f17f6b9af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-7bb1-a99e-70dc56c788cc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7354-b795-9f4f17f6b9af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019e4af3-d2a0-75be-8df3-645bf096f2c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7354-b795-9f4f17f6b9af" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019e4af3-d2a0-75be-8df3-645bf096f2c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e4af3-d2a0-7050-a071-54a61aaa4675" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7354-b795-9f4f17f6b9af" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e4af3-d2a0-7050-a071-54a61aaa4675" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e4af3-d2a0-739e-80ca-e0c710d71317" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7354-b795-9f4f17f6b9af" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e4af3-d2a0-739e-80ca-e0c710d71317" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-709f-ac6c-2c83266f16ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-7b1b-a9ab-6f633757665b" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-709f-ac6c-2c83266f16ad" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-709f-ac6c-2c83266f16ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-709f-ac6c-2c83266f16ad" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-709f-ac6c-2c83266f16ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-709f-ac6c-2c83266f16ad" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019e4af3-d2a0-7062-bb20-2b65ec5ba01b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019e4af3-d2a0-7062-bb20-2b65ec5ba01b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_019e4af3-d2a0-7d45-8f13-3cf7df4ab7ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_019e4af3-d2a0-7d45-8f13-3cf7df4ab7ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019e4af3-d2a0-77e7-beeb-9ab951d4c30e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_019e4af3-d2a0-77e7-beeb-9ab951d4c30e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-78a9-9b21-0ead98db118e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_019e4af3-d2a0-78a9-9b21-0ead98db118e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019e4af3-d2a0-71e5-8669-7f5f3a88c1bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:to="loc_us-gaap_CommercialMortgageBackedSecuritiesMember_019e4af3-d2a0-71e5-8669-7f5f3a88c1bc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_OtherAssetBackedSecuritiesMember_019e4af3-d2a0-7824-8a7c-8ed89023232d" xlink:href="arx-20260630.xsd#arx_OtherAssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7164-a0a5-677e50a7f1aa" xlink:to="loc_arx_OtherAssetBackedSecuritiesMember_019e4af3-d2a0-7824-8a7c-8ed89023232d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d2a0-7672-b825-87c520547d9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4af3-d2a0-746d-adfb-3c14ddc734fa" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019e4af3-d2a0-7672-b825-87c520547d9f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/FairvaluemeasurementsScheduleofAssetsMeasuredatFairValueonNonRecurringBasisDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#FairvaluemeasurementsScheduleofAssetsMeasuredatFairValueonNonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/FairvaluemeasurementsScheduleofAssetsMeasuredatFairValueonNonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4af3-d2a0-73c3-a06c-ed511da77c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-71ed-882c-cc4cfae7a4fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4af3-d2a0-73c3-a06c-ed511da77c4d" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-71ed-882c-cc4cfae7a4fd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-788e-b2af-7c5fd91ea626" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-71ed-882c-cc4cfae7a4fd" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-788e-b2af-7c5fd91ea626" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-788e-b2af-7c5fd91ea626_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-788e-b2af-7c5fd91ea626" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-788e-b2af-7c5fd91ea626_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-72f2-bc22-392088d73da2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4af3-d2a0-788e-b2af-7c5fd91ea626" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-72f2-bc22-392088d73da2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019e4af3-d2a0-7160-8e82-d2d7d1ffd0ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsNonrecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4af3-d2a0-72f2-bc22-392088d73da2" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019e4af3-d2a0-7160-8e82-d2d7d1ffd0ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-75e5-a7bb-251983cb6868" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-71ed-882c-cc4cfae7a4fd" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-75e5-a7bb-251983cb6868" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-75e5-a7bb-251983cb6868_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-75e5-a7bb-251983cb6868" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-75e5-a7bb-251983cb6868_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7cd1-af8f-816c196655b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4af3-d2a0-75e5-a7bb-251983cb6868" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7cd1-af8f-816c196655b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019e4af3-d2a0-782f-a759-839f75cdb8c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7cd1-af8f-816c196655b1" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019e4af3-d2a0-782f-a759-839f75cdb8c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e4af3-d2a0-7b54-8f5d-2c4441f9123e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7cd1-af8f-816c196655b1" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e4af3-d2a0-7b54-8f5d-2c4441f9123e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e4af3-d2a0-7926-98a1-0918b510d20b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4af3-d2a0-7cd1-af8f-816c196655b1" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e4af3-d2a0-7926-98a1-0918b510d20b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7232-8d42-258172299bc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4af3-d2a0-71ed-882c-cc4cfae7a4fd" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7232-8d42-258172299bc2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7232-8d42-258172299bc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7232-8d42-258172299bc2" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7232-8d42-258172299bc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7f3f-b9ae-34a1f14ab294" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4af3-d2a0-7232-8d42-258172299bc2" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7f3f-b9ae-34a1f14ab294" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MGAsAndTPAsMember_019e4af3-d2a0-72df-be41-3435dae99b9a" xlink:href="arx-20260630.xsd#arx_MGAsAndTPAsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7f3f-b9ae-34a1f14ab294" xlink:to="loc_arx_MGAsAndTPAsMember_019e4af3-d2a0-72df-be41-3435dae99b9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_VentureFundsMember_019e4af3-d2a0-7d93-82d8-7c4dfc69435f" xlink:href="arx-20260630.xsd#arx_VentureFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4af3-d2a0-7f3f-b9ae-34a1f14ab294" xlink:to="loc_arx_VentureFundsMember_019e4af3-d2a0-7d93-82d8-7c4dfc69435f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d2a0-77f4-b2f4-9fd77f038fb8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4af3-d2a0-73c3-a06c-ed511da77c4d" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d2a0-77f4-b2f4-9fd77f038fb8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/ReinsuranceNarrativeDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#ReinsuranceNarrativeDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/ReinsuranceNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskLineItems_019e4af3-d34a-74dc-a051-8a4f91f77e7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CededCreditRiskTable_019e4af3-d34a-7cd2-a78a-6ea24e9d14ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CededCreditRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CededCreditRiskLineItems_019e4af3-d34a-74dc-a051-8a4f91f77e7b" xlink:to="loc_us-gaap_CededCreditRiskTable_019e4af3-d34a-7cd2-a78a-6ea24e9d14ce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestAxis_019e4af3-d34a-7842-a3d1-4daa2eea17ce" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_019e4af3-d34a-7cd2-a78a-6ea24e9d14ce" xlink:to="loc_srt_CreditRatingAMBestAxis_019e4af3-d34a-7842-a3d1-4daa2eea17ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestDomain_019e4af3-d34a-7842-a3d1-4daa2eea17ce_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CreditRatingAMBestAxis_019e4af3-d34a-7842-a3d1-4daa2eea17ce" xlink:to="loc_srt_CreditRatingAMBestDomain_019e4af3-d34a-7842-a3d1-4daa2eea17ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingAMBestDomain_019e4af3-d34a-7512-8848-29dae30ca017" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CreditRatingAMBestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CreditRatingAMBestAxis_019e4af3-d34a-7842-a3d1-4daa2eea17ce" xlink:to="loc_srt_CreditRatingAMBestDomain_019e4af3-d34a-7512-8848-29dae30ca017" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AMBestAMinusRatingMember_019e4af3-d34a-7dad-acb1-09adc0d92345" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AMBestAMinusRatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CreditRatingAMBestDomain_019e4af3-d34a-7512-8848-29dae30ca017" xlink:to="loc_srt_AMBestAMinusRatingMember_019e4af3-d34a-7dad-acb1-09adc0d92345" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4af3-d34a-70f2-bfd1-ab4470e4df26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_019e4af3-d34a-7cd2-a78a-6ea24e9d14ce" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4af3-d34a-70f2-bfd1-ab4470e4df26" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4af3-d34a-70f2-bfd1-ab4470e4df26_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4af3-d34a-70f2-bfd1-ab4470e4df26" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4af3-d34a-70f2-bfd1-ab4470e4df26_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4af3-d34a-79cc-a8f5-378e0d71ce16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4af3-d34a-70f2-bfd1-ab4470e4df26" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4af3-d34a-79cc-a8f5-378e0d71ce16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverableMember_019e4af3-d34a-7ed7-b306-773a3c27024e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4af3-d34a-79cc-a8f5-378e0d71ce16" xlink:to="loc_us-gaap_ReinsuranceRecoverableMember_019e4af3-d34a-7ed7-b306-773a3c27024e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4af3-d34a-70b8-bf92-37d27eb9cb96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CededCreditRiskTable_019e4af3-d34a-7cd2-a78a-6ea24e9d14ce" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4af3-d34a-70b8-bf92-37d27eb9cb96" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e4af3-d34a-70b8-bf92-37d27eb9cb96_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4af3-d34a-70b8-bf92-37d27eb9cb96" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e4af3-d34a-70b8-bf92-37d27eb9cb96_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e4af3-d34a-78d3-b238-8e4b36c1e622" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4af3-d34a-70b8-bf92-37d27eb9cb96" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e4af3-d34a-78d3-b238-8e4b36c1e622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsurerConcentrationRiskMember_019e4af3-d34a-7d9e-a815-6d06e7c45cd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsurerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019e4af3-d34a-78d3-b238-8e4b36c1e622" xlink:to="loc_us-gaap_ReinsurerConcentrationRiskMember_019e4af3-d34a-7d9e-a815-6d06e7c45cd2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019e4af3-d34a-79fc-a6d0-861e263e190c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskLineItems_019e4af3-d34a-74dc-a051-8a4f91f77e7b" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019e4af3-d34a-79fc-a6d0-861e263e190c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReinsuranceRecoverablesAllowance_019e4af3-d34a-7a30-82f5-63e6cc6d8f85" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReinsuranceRecoverablesAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CededCreditRiskLineItems_019e4af3-d34a-74dc-a051-8a4f91f77e7b" xlink:to="loc_us-gaap_ReinsuranceRecoverablesAllowance_019e4af3-d34a-7a30-82f5-63e6cc6d8f85" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/DebtScheduleofDebtOutstandingDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#DebtScheduleofDebtOutstandingDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/DebtScheduleofDebtOutstandingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-7128-a96d-c68d15bccd91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-770a-94e3-e1fd89abf7f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-7128-a96d-c68d15bccd91" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-770a-94e3-e1fd89abf7f9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7c17-ac9f-a44b808bd1ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-770a-94e3-e1fd89abf7f9" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7c17-ac9f-a44b808bd1ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7c17-ac9f-a44b808bd1ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7c17-ac9f-a44b808bd1ce" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7c17-ac9f-a44b808bd1ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-71d8-b623-1478af059bd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7c17-ac9f-a44b808bd1ce" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-71d8-b623-1478af059bd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_SeniorUnsecuredNotesMember_019e4af3-d34a-7f73-8b7a-93a909a7dae7" xlink:href="arx-20260630.xsd#arx_SeniorUnsecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-71d8-b623-1478af059bd9" xlink:to="loc_arx_SeniorUnsecuredNotesMember_019e4af3-d34a-7f73-8b7a-93a909a7dae7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-74fe-9609-4c8c11d26d28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-770a-94e3-e1fd89abf7f9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-74fe-9609-4c8c11d26d28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-74fe-9609-4c8c11d26d28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-74fe-9609-4c8c11d26d28" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-74fe-9609-4c8c11d26d28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-7335-a6a2-5fe3dfb49769" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-74fe-9609-4c8c11d26d28" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-7335-a6a2-5fe3dfb49769" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4af3-d34a-7942-971a-45313df661d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-7335-a6a2-5fe3dfb49769" xlink:to="loc_us-gaap_LineOfCreditMember_019e4af3-d34a-7942-971a-45313df661d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019e4af3-d34a-7f80-9d67-219394985b96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-7128-a96d-c68d15bccd91" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019e4af3-d34a-7f80-9d67-219394985b96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_019e4af3-d34a-71b8-a70d-61b52daa0602" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-7128-a96d-c68d15bccd91" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_019e4af3-d34a-71b8-a70d-61b52daa0602" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e4af3-d34a-7ff7-9d23-b097455eb514" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-7128-a96d-c68d15bccd91" xlink:to="loc_us-gaap_LongTermDebt_019e4af3-d34a-7ff7-9d23-b097455eb514" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/DebtNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-717e-bb2e-56aef1ed37a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-7dcf-b0c7-19def0ffc978" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-717e-bb2e-56aef1ed37a4" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-7dcf-b0c7-19def0ffc978" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4af3-d34a-7752-8c9e-78acbbc5a77b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-7dcf-b0c7-19def0ffc978" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4af3-d34a-7752-8c9e-78acbbc5a77b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4af3-d34a-7752-8c9e-78acbbc5a77b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4af3-d34a-7752-8c9e-78acbbc5a77b" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4af3-d34a-7752-8c9e-78acbbc5a77b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4af3-d34a-75ea-bb53-8bc239f87452" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4af3-d34a-7752-8c9e-78acbbc5a77b" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4af3-d34a-75ea-bb53-8bc239f87452" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e4af3-d34a-705a-a58f-7b60c00f6596" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4af3-d34a-75ea-bb53-8bc239f87452" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e4af3-d34a-705a-a58f-7b60c00f6596" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-7fe6-8225-c83e904b73e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-7dcf-b0c7-19def0ffc978" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-7fe6-8225-c83e904b73e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-7fe6-8225-c83e904b73e0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-7fe6-8225-c83e904b73e0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-7fe6-8225-c83e904b73e0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-733c-a6ff-5e61ad161c20" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4af3-d34a-7fe6-8225-c83e904b73e0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-733c-a6ff-5e61ad161c20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4af3-d34a-7ac4-a7ae-9cc184f5ae45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4af3-d34a-733c-a6ff-5e61ad161c20" xlink:to="loc_us-gaap_LineOfCreditMember_019e4af3-d34a-7ac4-a7ae-9cc184f5ae45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7666-9aea-2b907c277df1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-7dcf-b0c7-19def0ffc978" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7666-9aea-2b907c277df1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7666-9aea-2b907c277df1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7666-9aea-2b907c277df1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7666-9aea-2b907c277df1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7bf8-a036-84f0f2b4f59d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4af3-d34a-7666-9aea-2b907c277df1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7bf8-a036-84f0f2b4f59d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_DelayedDrawTermLoansMember_019e4af3-d34a-780a-adf9-1330018eb668" xlink:href="arx-20260630.xsd#arx_DelayedDrawTermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7bf8-a036-84f0f2b4f59d" xlink:to="loc_arx_DelayedDrawTermLoansMember_019e4af3-d34a-780a-adf9-1330018eb668" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_SeniorUnsecuredNotesMember_019e4af3-d34a-726a-b8c7-cc5010f2abdf" xlink:href="arx-20260630.xsd#arx_SeniorUnsecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4af3-d34a-7bf8-a036-84f0f2b4f59d" xlink:to="loc_arx_SeniorUnsecuredNotesMember_019e4af3-d34a-726a-b8c7-cc5010f2abdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4af3-d34a-7f71-a5fa-9d0f18b90955" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4af3-d34a-7dcf-b0c7-19def0ffc978" xlink:to="loc_srt_RangeAxis_019e4af3-d34a-7f71-a5fa-9d0f18b90955" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4af3-d34a-7f71-a5fa-9d0f18b90955_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4af3-d34a-7f71-a5fa-9d0f18b90955" xlink:to="loc_srt_RangeMember_019e4af3-d34a-7f71-a5fa-9d0f18b90955_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4af3-d34a-774a-9a76-6254dcff0b69" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4af3-d34a-7f71-a5fa-9d0f18b90955" xlink:to="loc_srt_RangeMember_019e4af3-d34a-774a-9a76-6254dcff0b69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4af3-d34a-7533-b2f9-5debfc05c94c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4af3-d34a-774a-9a76-6254dcff0b69" xlink:to="loc_srt_MinimumMember_019e4af3-d34a-7533-b2f9-5debfc05c94c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4af3-d34a-77af-8719-04e99a1514fa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4af3-d34a-774a-9a76-6254dcff0b69" xlink:to="loc_srt_MaximumMember_019e4af3-d34a-77af-8719-04e99a1514fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4af3-d34a-7f73-9780-6a4773409f2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-717e-bb2e-56aef1ed37a4" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4af3-d34a-7f73-9780-6a4773409f2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_LineOfCreditFacilityMaximumBorrowingCapacityAccordionFeature_019e4af3-d34a-7018-acb0-7ade7284337b" xlink:href="arx-20260630.xsd#arx_LineOfCreditFacilityMaximumBorrowingCapacityAccordionFeature"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-717e-bb2e-56aef1ed37a4" xlink:to="loc_arx_LineOfCreditFacilityMaximumBorrowingCapacityAccordionFeature_019e4af3-d34a-7018-acb0-7ade7284337b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4af3-d34a-7b1a-aa52-1a135b8a40a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-717e-bb2e-56aef1ed37a4" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4af3-d34a-7b1a-aa52-1a135b8a40a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019e4af3-d34a-7b0b-ac70-8b93a8b91cdb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4af3-d34a-717e-bb2e-56aef1ed37a4" xlink:to="loc_us-gaap_InterestExpenseDebt_019e4af3-d34a-7b0b-ac70-8b93a8b91cdb" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/EquityNarrativeDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#EquityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/EquityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019fa7ad-7c56-71c0-b59c-544af52689f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019fa7ad-7c56-71c0-b59c-544af52689f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019fa7ad-a65a-7e38-99e6-e3584d678a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019fa7ad-7c56-71c0-b59c-544af52689f2" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019fa7ad-a65a-7e38-99e6-e3584d678a4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019fa7ad-a65a-7e38-99e6-e3584d678a4b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019fa7ad-a65a-7e38-99e6-e3584d678a4b" xlink:to="loc_us-gaap_ClassOfStockDomain_019fa7ad-a65a-7e38-99e6-e3584d678a4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019fa7ad-a65a-7789-9903-50df237cc877" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019fa7ad-a65a-7e38-99e6-e3584d678a4b" xlink:to="loc_us-gaap_ClassOfStockDomain_019fa7ad-a65a-7789-9903-50df237cc877" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019fa7ad-a65a-78ef-b149-bf7961a58bc6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019fa7ad-a65a-7789-9903-50df237cc877" xlink:to="loc_us-gaap_CommonClassAMember_019fa7ad-a65a-78ef-b149-bf7961a58bc6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019fa7ad-a65a-7414-89cf-701b39188b1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019fa7ad-a65a-7789-9903-50df237cc877" xlink:to="loc_us-gaap_CommonClassBMember_019fa7ad-a65a-7414-89cf-701b39188b1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_019fa7ad-f0d2-7238-a585-7a7cacf78277" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019fa7ad-7c56-71c0-b59c-544af52689f2" xlink:to="loc_srt_ShareRepurchaseProgramAxis_019fa7ad-f0d2-7238-a585-7a7cacf78277" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019fa7ad-f0d2-7238-a585-7a7cacf78277_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019fa7ad-f0d2-7238-a585-7a7cacf78277" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019fa7ad-f0d2-7238-a585-7a7cacf78277_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019fa7ad-f0d2-7999-8815-fe2d77390d28" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019fa7ad-f0d2-7238-a585-7a7cacf78277" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019fa7ad-f0d2-7999-8815-fe2d77390d28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_March2026RepurchaseProgramMember_019fa7ad-f0d2-7c5e-9acf-02f55df1d69f" xlink:href="arx-20260630.xsd#arx_March2026RepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019fa7ad-f0d2-7999-8815-fe2d77390d28" xlink:to="loc_arx_March2026RepurchaseProgramMember_019fa7ad-f0d2-7c5e-9acf-02f55df1d69f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_NumberOfClassesOfCommonStock_019fa7ad-7c56-734a-a135-4ee741b56448" xlink:href="arx-20260630.xsd#arx_NumberOfClassesOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_arx_NumberOfClassesOfCommonStock_019fa7ad-7c56-734a-a135-4ee741b56448" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019fa7ad-7c56-77a9-b94d-48985207ba2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019fa7ad-7c56-77a9-b94d-48985207ba2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019fa7ad-a65a-769e-b195-edc3ebc15f88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019fa7ad-a65a-769e-b195-edc3ebc15f88" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_019fa7ad-f0d2-7323-80f4-d07299381f67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_019fa7ad-f0d2-7323-80f4-d07299381f67" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019fa7ad-f0d2-76fc-8f00-fe14b7d97d26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019fa7ad-f0d2-76fc-8f00-fe14b7d97d26" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019fa7ad-f0d2-71e9-8786-e309eb5810c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019fa7ad-f0d2-71e9-8786-e309eb5810c2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019fa7ad-f0d2-7f42-ac80-9e565fc71eb9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019fa7ad-f0d2-7f42-ac80-9e565fc71eb9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019fa7ad-f0d2-7884-87a6-23dcde2de9a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019fa7ad-f0d2-7884-87a6-23dcde2de9a4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019fa7ad-f0d2-7e17-b1c1-d9142318b832" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019fa7ad-f0d2-7e17-b1c1-d9142318b832" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019fa7ad-f0d2-7819-8410-e36dabf12267" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019fa7ad-f0d2-7819-8410-e36dabf12267" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019fa7ad-f0d2-7775-b282-a3d871b4ead8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019fa7ad-f0d2-7775-b282-a3d871b4ead8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019fa7ad-f0d2-7cb6-bc5d-dc4b423991ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019fa7ad-7c56-7aa2-9ed1-b160523c32a7" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019fa7ad-f0d2-7cb6-bc5d-dc4b423991ad" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/EquityScheduleofCommonStockIssuedandOutstandingRollForwardDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#EquityScheduleofCommonStockIssuedandOutstandingRollForwardDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/EquityScheduleofCommonStockIssuedandOutstandingRollForwardDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019e4af3-d34a-7261-90e7-a604bb7e3917" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019e4af3-d34a-727d-8886-6e943d8fefaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4af3-d34a-7261-90e7-a604bb7e3917" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019e4af3-d34a-727d-8886-6e943d8fefaf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d34a-7485-a0e2-522c4147acb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e4af3-d34a-727d-8886-6e943d8fefaf" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d34a-7485-a0e2-522c4147acb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d34a-7485-a0e2-522c4147acb1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d34a-7485-a0e2-522c4147acb1" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d34a-7485-a0e2-522c4147acb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4af3-d34a-7fac-99a8-6907a6cbc67d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4af3-d34a-7485-a0e2-522c4147acb1" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4af3-d34a-7fac-99a8-6907a6cbc67d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4af3-d34a-7939-b137-2bf098d8536b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d34a-7fac-99a8-6907a6cbc67d" xlink:to="loc_us-gaap_CommonClassAMember_019e4af3-d34a-7939-b137-2bf098d8536b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4af3-d34a-7ccf-a827-f426ec0a76b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4af3-d34a-7fac-99a8-6907a6cbc67d" xlink:to="loc_us-gaap_CommonClassBMember_019e4af3-d34a-7ccf-a827-f426ec0a76b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d34a-7da9-86c6-f7d64357c0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e4af3-d34a-727d-8886-6e943d8fefaf" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d34a-7da9-86c6-f7d64357c0dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4af3-d34a-7da9-86c6-f7d64357c0dc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d34a-7da9-86c6-f7d64357c0dc" xlink:to="loc_us-gaap_EquityComponentDomain_019e4af3-d34a-7da9-86c6-f7d64357c0dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4af3-d34a-7881-a4dd-4678be59b4b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4af3-d34a-7da9-86c6-f7d64357c0dc" xlink:to="loc_us-gaap_EquityComponentDomain_019e4af3-d34a-7881-a4dd-4678be59b4b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e4af3-d34a-7fd9-9c8b-398054b66128" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4af3-d34a-7881-a4dd-4678be59b4b2" xlink:to="loc_us-gaap_CommonStockMember_019e4af3-d34a-7fd9-9c8b-398054b66128" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d34a-73a9-bc10-f52973dc6b6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4af3-d34a-7261-90e7-a604bb7e3917" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d34a-73a9-bc10-f52973dc6b6d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4af3-d34a-78ef-ad87-50f0d88125ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d34a-73a9-bc10-f52973dc6b6d" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e4af3-d34a-78ef-ad87-50f0d88125ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_019e4af3-d34a-7da2-9bce-fee7c8e581e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d34a-73a9-bc10-f52973dc6b6d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_019e4af3-d34a-7da2-9bce-fee7c8e581e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019e4af3-d34a-7cf8-b920-80d6e3c2586d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d34a-73a9-bc10-f52973dc6b6d" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019e4af3-d34a-7cf8-b920-80d6e3c2586d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019e4af3-d34a-7ea1-8f80-206d6ce5bc91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4af3-d34a-73a9-bc10-f52973dc6b6d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019e4af3-d34a-7ea1-8f80-206d6ce5bc91" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4af3-d34a-73b3-8631-69f685344a06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SharebasedcompensationSummaryofSharebasedCompensationDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SharebasedcompensationSummaryofSharebasedCompensationDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SharebasedcompensationSummaryofSharebasedCompensationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-75e7-a7ca-04078b54ba18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7a96-ba14-09c84ab97bcb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-75e7-a7ca-04078b54ba18" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7a96-ba14-09c84ab97bcb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-725e-8570-e0010630bf9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7a96-ba14-09c84ab97bcb" xlink:to="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-725e-8570-e0010630bf9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-725e-8570-e0010630bf9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-725e-8570-e0010630bf9b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-725e-8570-e0010630bf9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7cc7-8757-1c82e76adeb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-725e-8570-e0010630bf9b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7cc7-8757-1c82e76adeb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019e4af3-d34a-732c-b4a0-1ce88aefcb3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7cc7-8757-1c82e76adeb1" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019e4af3-d34a-732c-b4a0-1ce88aefcb3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4af3-d34a-73fb-8559-17d6675ea33f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7cc7-8757-1c82e76adeb1" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4af3-d34a-73fb-8559-17d6675ea33f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_019e4af3-d34a-74bf-b961-d67556f788c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7cc7-8757-1c82e76adeb1" xlink:to="loc_us-gaap_EmployeeStockMember_019e4af3-d34a-74bf-b961-d67556f788c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_LiabilityClassifiedAwardsMember_019e4af3-d34a-7f4f-a951-d1064916780f" xlink:href="arx-20260630.xsd#arx_LiabilityClassifiedAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7cc7-8757-1c82e76adeb1" xlink:to="loc_arx_LiabilityClassifiedAwardsMember_019e4af3-d34a-7f4f-a951-d1064916780f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4af3-d34a-7ddb-9e1a-ab41175bda9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-75e7-a7ca-04078b54ba18" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4af3-d34a-7ddb-9e1a-ab41175bda9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_019e4af3-d34a-7d46-8dcb-64aa9b09b153" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-75e7-a7ca-04078b54ba18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost_019e4af3-d34a-7d46-8dcb-64aa9b09b153" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber_019e4af3-d34a-7328-930d-eae2b52ac70f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-75e7-a7ca-04078b54ba18" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAcceleratedVestingNumber_019e4af3-d34a-7328-930d-eae2b52ac70f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SharebasedcompensationNarrativeDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SharebasedcompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SharebasedcompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7119-bfc8-8d058ee7d78c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7119-bfc8-8d058ee7d78c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-74dd-aed2-fcc84c560c85" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7119-bfc8-8d058ee7d78c" xlink:to="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-74dd-aed2-fcc84c560c85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-74dd-aed2-fcc84c560c85_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-74dd-aed2-fcc84c560c85" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-74dd-aed2-fcc84c560c85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-74dd-aed2-fcc84c560c85" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019e4af3-d34a-7cb9-9622-6e2603afe2dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019e4af3-d34a-7cb9-9622-6e2603afe2dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4af3-d34a-7626-b2a1-0425ae422a03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4af3-d34a-7626-b2a1-0425ae422a03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_019e4af3-d34a-7d8b-bcb6-8982ddf8d482" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:to="loc_us-gaap_EmployeeStockMember_019e4af3-d34a-7d8b-bcb6-8982ddf8d482" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_LiabilityClassifiedAwardsMember_019e4af3-d34a-764d-9f15-c866dd6979e2" xlink:href="arx-20260630.xsd#arx_LiabilityClassifiedAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:to="loc_arx_LiabilityClassifiedAwardsMember_019e4af3-d34a-764d-9f15-c866dd6979e2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019fd7e6-2045-78f7-9b39-6f3c797770aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-7300-9892-633ff5bfd263" xlink:to="loc_us-gaap_PerformanceSharesMember_019fd7e6-2045-78f7-9b39-6f3c797770aa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019fd7e6-8e95-742a-9350-0894701d7f87" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019e4af3-d34a-7119-bfc8-8d058ee7d78c" xlink:to="loc_srt_RangeAxis_019fd7e6-8e95-742a-9350-0894701d7f87" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019fd7e6-8e95-742a-9350-0894701d7f87_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019fd7e6-8e95-742a-9350-0894701d7f87" xlink:to="loc_srt_RangeMember_019fd7e6-8e95-742a-9350-0894701d7f87_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019fd7e6-8e95-76e6-81d5-9182bba18f49" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019fd7e6-8e95-742a-9350-0894701d7f87" xlink:to="loc_srt_RangeMember_019fd7e6-8e95-76e6-81d5-9182bba18f49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019fd7e6-b5d5-7c56-8db9-93ecb881de1c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019fd7e6-8e95-76e6-81d5-9182bba18f49" xlink:to="loc_srt_MinimumMember_019fd7e6-b5d5-7c56-8db9-93ecb881de1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019fd7e6-d365-7e89-bea1-6373675003fb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019fd7e6-8e95-76e6-81d5-9182bba18f49" xlink:to="loc_srt_MaximumMember_019fd7e6-d365-7e89-bea1-6373675003fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4af3-d34a-7135-b256-93019c236233" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4af3-d34a-7135-b256-93019c236233" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_019e4af3-d34a-711d-bfe8-2bcaad264a6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_019e4af3-d34a-711d-bfe8-2bcaad264a6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019e4af3-d34a-78b6-b91f-23a6fd0f04a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019e4af3-d34a-78b6-b91f-23a6fd0f04a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_019e4af3-d34a-74e4-9654-172e731a1bce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_019e4af3-d34a-74e4-9654-172e731a1bce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetPercent_019fd7e5-e67d-7624-9a94-6b15e2247819" xlink:href="arx-20260630.xsd#arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardTargetPercent_019fd7e5-e67d-7624-9a94-6b15e2247819" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsLiability_019e4af3-d34a-7f36-98bc-2a74726fc5c8" xlink:href="arx-20260630.xsd#arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsLiability_019e4af3-d34a-7f36-98bc-2a74726fc5c8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformancePeriod_019fdcf0-8e71-7c82-8c7b-d0b610c62ede" xlink:href="arx-20260630.xsd#arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformancePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019e4af3-d34a-711d-b2c4-f36fa2257ebc" xlink:to="loc_arx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformancePeriod_019fdcf0-8e71-7c82-8c7b-d0b610c62ede" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SharebasedcompensationScheduleofUnvestedRSUsDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SharebasedcompensationScheduleofUnvestedRSUsDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SharebasedcompensationScheduleofUnvestedRSUsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4af3-d34a-7dfe-8507-e49a982a71d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4af3-d34a-79a2-a22f-a62c68f98592" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4af3-d34a-7dfe-8507-e49a982a71d1" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4af3-d34a-79a2-a22f-a62c68f98592" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-72d7-a562-cba733a7f0ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4af3-d34a-79a2-a22f-a62c68f98592" xlink:to="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-72d7-a562-cba733a7f0ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-72d7-a562-cba733a7f0ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-72d7-a562-cba733a7f0ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-72d7-a562-cba733a7f0ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-70d8-9d16-2c5d365c8df7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4af3-d34a-72d7-a562-cba733a7f0ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-70d8-9d16-2c5d365c8df7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4af3-d34a-72dd-831c-33395a990c8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4af3-d34a-70d8-9d16-2c5d365c8df7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4af3-d34a-72dd-831c-33395a990c8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e4af3-d34a-7f7d-bf3b-b87ad91096db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4af3-d34a-7dfe-8507-e49a982a71d1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e4af3-d34a-7f7d-bf3b-b87ad91096db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e4af3-d34a-7195-91f1-f37a3df0851c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e4af3-d34a-7f7d-bf3b-b87ad91096db" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e4af3-d34a-7195-91f1-f37a3df0851c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019e4af3-d34a-792e-b98f-fbf478b921d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e4af3-d34a-7f7d-bf3b-b87ad91096db" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019e4af3-d34a-792e-b98f-fbf478b921d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019e4af3-d34a-7c7f-bc08-854b439f6d0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e4af3-d34a-7f7d-bf3b-b87ad91096db" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019e4af3-d34a-7c7f-bc08-854b439f6d0a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019e4af3-d34a-7aaa-9356-48760b6896f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019e4af3-d34a-7f7d-bf3b-b87ad91096db" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019e4af3-d34a-7aaa-9356-48760b6896f4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e4af3-d34a-768a-a19d-2e106f8eb11b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e4af3-d34a-7c56-be29-d0cb1c9f8b84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4af3-d34a-7dfe-8507-e49a982a71d1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e4af3-d34a-7c56-be29-d0cb1c9f8b84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e4af3-d34a-73a0-9a25-357051afa2a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e4af3-d34a-7c56-be29-d0cb1c9f8b84" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e4af3-d34a-73a0-9a25-357051afa2a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e4af3-d34a-7d05-b526-b1f8b680ede8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e4af3-d34a-7c56-be29-d0cb1c9f8b84" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e4af3-d34a-7d05-b526-b1f8b680ede8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019e4af3-d34a-75eb-ac00-939312e7e0d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e4af3-d34a-7c56-be29-d0cb1c9f8b84" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019e4af3-d34a-75eb-ac00-939312e7e0d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019e4af3-d34a-7bdc-88d5-ce2c95580744" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019e4af3-d34a-7c56-be29-d0cb1c9f8b84" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019e4af3-d34a-7bdc-88d5-ce2c95580744" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e4af3-d34a-71e2-b6e0-3d9a7457bc69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/IncometaxesScheduleofCompositionofEffectiveTaxRatesDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#IncometaxesScheduleofCompositionofEffectiveTaxRatesDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/IncometaxesScheduleofCompositionofEffectiveTaxRatesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019e4af3-d34a-711d-b9da-6c7d2e60d8d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019e4af3-d34a-73f7-9f90-2ba0bbbe8f04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019e4af3-d34a-711d-b9da-6c7d2e60d8d2" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019e4af3-d34a-73f7-9f90-2ba0bbbe8f04" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_IncomeTaxPayingStatusAxis_019e4af3-d34a-72bc-b111-7aed7fa9b21d" xlink:href="arx-20260630.xsd#arx_IncomeTaxPayingStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTable_019e4af3-d34a-73f7-9f90-2ba0bbbe8f04" xlink:to="loc_arx_IncomeTaxPayingStatusAxis_019e4af3-d34a-72bc-b111-7aed7fa9b21d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_IncomeTaxPayingStatusDomain_019e4af3-d34a-72bc-b111-7aed7fa9b21d_default" xlink:href="arx-20260630.xsd#arx_IncomeTaxPayingStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_arx_IncomeTaxPayingStatusAxis_019e4af3-d34a-72bc-b111-7aed7fa9b21d" xlink:to="loc_arx_IncomeTaxPayingStatusDomain_019e4af3-d34a-72bc-b111-7aed7fa9b21d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_IncomeTaxPayingStatusDomain_019e4af3-d34a-74b8-861f-062ba23c03dc" xlink:href="arx-20260630.xsd#arx_IncomeTaxPayingStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_arx_IncomeTaxPayingStatusAxis_019e4af3-d34a-72bc-b111-7aed7fa9b21d" xlink:to="loc_arx_IncomeTaxPayingStatusDomain_019e4af3-d34a-74b8-861f-062ba23c03dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_TaxPayingEntitiesMember_019e4af3-d34a-7f8f-9ea7-e2d19be72185" xlink:href="arx-20260630.xsd#arx_TaxPayingEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_arx_IncomeTaxPayingStatusDomain_019e4af3-d34a-74b8-861f-062ba23c03dc" xlink:to="loc_arx_TaxPayingEntitiesMember_019e4af3-d34a-7f8f-9ea7-e2d19be72185" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_NonTaxPayingEntitiesMember_019e4af3-d34a-7781-8219-aab18d830350" xlink:href="arx-20260630.xsd#arx_NonTaxPayingEntitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_arx_IncomeTaxPayingStatusDomain_019e4af3-d34a-74b8-861f-062ba23c03dc" xlink:to="loc_arx_NonTaxPayingEntitiesMember_019e4af3-d34a-7781-8219-aab18d830350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e4af3-d34a-7c5d-9ba9-7a6baf6beb77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019e4af3-d34a-711d-b9da-6c7d2e60d8d2" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e4af3-d34a-7c5d-9ba9-7a6baf6beb77" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019e4af3-d34a-7ee0-bf81-2fd59c7b500c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019e4af3-d34a-711d-b9da-6c7d2e60d8d2" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019e4af3-d34a-7ee0-bf81-2fd59c7b500c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019e4af3-d34a-7294-a27a-1d7a0b09fcfd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_019e4af3-d34a-711d-b9da-6c7d2e60d8d2" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_019e4af3-d34a-7294-a27a-1d7a0b09fcfd" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/RelatedpartytransactionsDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#RelatedpartytransactionsDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/RelatedpartytransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4af3-d34a-7ccf-aa91-c9e83b460c43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4af3-d34a-7960-82b0-4ce402da1fde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4af3-d34a-7ccf-aa91-c9e83b460c43" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4af3-d34a-7960-82b0-4ce402da1fde" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d34a-7ccb-903b-1021c707ea94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4af3-d34a-7960-82b0-4ce402da1fde" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d34a-7ccb-903b-1021c707ea94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4af3-d34a-7ccb-903b-1021c707ea94_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d34a-7ccb-903b-1021c707ea94" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4af3-d34a-7ccb-903b-1021c707ea94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4af3-d34a-7ed1-bf93-371a6807a2bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4af3-d34a-7ccb-903b-1021c707ea94" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4af3-d34a-7ed1-bf93-371a6807a2bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_019e4af3-d34a-7da6-80b4-42135a833758" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4af3-d34a-7ed1-bf93-371a6807a2bf" xlink:to="loc_srt_AffiliatedEntityMember_019e4af3-d34a-7da6-80b4-42135a833758" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4af3-d34a-74f5-a058-ac13fcdbf4b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4af3-d34a-7ed1-bf93-371a6807a2bf" xlink:to="loc_us-gaap_RelatedPartyMember_019e4af3-d34a-74f5-a058-ac13fcdbf4b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_019e4af3-d34a-72de-9834-ded3a8b912bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAmountsOfTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4af3-d34a-7ccf-aa91-c9e83b460c43" xlink:to="loc_us-gaap_RelatedPartyTransactionAmountsOfTransaction_019e4af3-d34a-72de-9834-ded3a8b912bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PremiumsWrittenGross_019e4af3-d34a-716d-929a-c0ae9459ce10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PremiumsWrittenGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4af3-d34a-7ccf-aa91-c9e83b460c43" xlink:to="loc_us-gaap_PremiumsWrittenGross_019e4af3-d34a-716d-929a-c0ae9459ce10" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/CommitmentsandcontingenciesDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#CommitmentsandcontingenciesDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/CommitmentsandcontingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_019e4af3-d34a-7f78-a129-0b37158372bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable_019e4af3-d34a-7944-9ce0-627d3c5856a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019e4af3-d34a-7f78-a129-0b37158372bd" xlink:to="loc_us-gaap_OtherCommitmentsTable_019e4af3-d34a-7944-9ce0-627d3c5856a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_019e4af3-d34a-7931-95c2-0fbd840dd4f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_019e4af3-d34a-7944-9ce0-627d3c5856a2" xlink:to="loc_us-gaap_OtherCommitmentsAxis_019e4af3-d34a-7931-95c2-0fbd840dd4f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_019e4af3-d34a-7931-95c2-0fbd840dd4f6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_019e4af3-d34a-7931-95c2-0fbd840dd4f6" xlink:to="loc_us-gaap_OtherCommitmentsDomain_019e4af3-d34a-7931-95c2-0fbd840dd4f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_019e4af3-d34a-7802-8225-54175ba1caab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_019e4af3-d34a-7931-95c2-0fbd840dd4f6" xlink:to="loc_us-gaap_OtherCommitmentsDomain_019e4af3-d34a-7802-8225-54175ba1caab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_UnfundedInvestmentCommitmentsMember_019e4af3-d34a-7785-bdcb-320853f28b6a" xlink:href="arx-20260630.xsd#arx_UnfundedInvestmentCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_019e4af3-d34a-7802-8225-54175ba1caab" xlink:to="loc_arx_UnfundedInvestmentCommitmentsMember_019e4af3-d34a-7785-bdcb-320853f28b6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_019e4af3-d34a-7a97-9e48-587c36fdff16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019e4af3-d34a-7f78-a129-0b37158372bd" xlink:to="loc_us-gaap_OtherCommitment_019e4af3-d34a-7a97-9e48-587c36fdff16" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://accelerant.ai/role/SubsequenteventsDetails" xlink:type="simple" xlink:href="arx-20260630.xsd#SubsequenteventsDetails"/>
  <link:definitionLink xlink:role="http://accelerant.ai/role/SubsequenteventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019e4af3-d34a-7e79-9f39-00466389b461" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_SubsequentEventTable_019e4af3-d34a-7e79-9f39-00466389b461" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019e4af3-d34a-789b-812d-61dabcc9b5d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019e4af3-d34a-7e79-9f39-00466389b461" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019e4af3-d34a-789b-812d-61dabcc9b5d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019e4af3-d34a-789b-812d-61dabcc9b5d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019e4af3-d34a-789b-812d-61dabcc9b5d4" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019e4af3-d34a-789b-812d-61dabcc9b5d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019e4af3-d34a-719b-b185-512b1dafdcf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019e4af3-d34a-789b-812d-61dabcc9b5d4" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019e4af3-d34a-719b-b185-512b1dafdcf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019e4af3-d34a-7001-8b0b-ea9f822ff59f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019e4af3-d34a-719b-b185-512b1dafdcf9" xlink:to="loc_us-gaap_SubsequentEventMember_019e4af3-d34a-7001-8b0b-ea9f822ff59f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019ffacd-2674-772d-8537-324c0bba7e8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019e4af3-d34a-7e79-9f39-00466389b461" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019ffacd-2674-772d-8537-324c0bba7e8f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019ffacd-2674-772d-8537-324c0bba7e8f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019ffacd-2674-772d-8537-324c0bba7e8f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019ffacd-2674-772d-8537-324c0bba7e8f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019ffacd-2674-7f56-8789-d2afe9d148f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019ffacd-2674-772d-8537-324c0bba7e8f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019ffacd-2674-7f56-8789-d2afe9d148f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_arx_MergerAgreementMember_019ffacd-d468-7122-ab18-6f5982ece389" xlink:href="arx-20260630.xsd#arx_MergerAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019ffacd-2674-7f56-8789-d2afe9d148f4" xlink:to="loc_arx_MergerAgreementMember_019ffacd-d468-7122-ab18-6f5982ece389" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019e4af3-d34a-7108-a321-8f3dd7b88ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019e4af3-d34a-7108-a321-8f3dd7b88ba1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d34a-71d0-876e-9017e716a748" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_019e4af3-d34a-71d0-876e-9017e716a748" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_019e4af3-d34a-7922-9a16-1b93aaf6a0e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_GainLossOnInvestments_019e4af3-d34a-7922-9a16-1b93aaf6a0e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019e4af3-d34a-7196-92b8-0a07079b6bff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019e4af3-d34a-7196-92b8-0a07079b6bff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019e4af3-d34a-73dd-9391-8d51c979cfbc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019e4af3-d34a-73dd-9391-8d51c979cfbc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e4af3-d34a-774d-a67b-1031e5621133" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e4af3-d34a-774d-a67b-1031e5621133" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionSharePrice_019ffab5-ffc3-7f1a-9ffc-3807de9a8c37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionSharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4af3-d34a-7120-a651-f855972f0952" xlink:to="loc_us-gaap_BusinessAcquisitionSharePrice_019ffab5-ffc3-7f1a-9ffc-3807de9a8c37" xlink:type="arc" order="6"/>
  </link:definitionLink>
</link:linkbase>
