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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019f6c2b-a781-76aa-94ae-0d6e0dd452e8,g:6bd089e0-44e4-4d59-b550-8bd3164719d6-->
<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://monroecap.com/role/Cover" xlink:type="simple" xlink:href="mcip-20260720.xsd#Cover"/>
  <link:definitionLink xlink:role="http://monroecap.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019f6c2b-a781-7a44-9388-80ca044bbd81" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_DocumentInformationTable_019f6c2b-a781-7a44-9388-80ca044bbd81" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressesAddressTypeAxis_019f6c2b-a781-749c-8d4d-52f2acb6bcc5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressesAddressTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019f6c2b-a781-7a44-9388-80ca044bbd81" xlink:to="loc_dei_EntityAddressesAddressTypeAxis_019f6c2b-a781-749c-8d4d-52f2acb6bcc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AddressTypeDomain_019f6c2b-a781-749c-8d4d-52f2acb6bcc5_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AddressTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_EntityAddressesAddressTypeAxis_019f6c2b-a781-749c-8d4d-52f2acb6bcc5" xlink:to="loc_dei_AddressTypeDomain_019f6c2b-a781-749c-8d4d-52f2acb6bcc5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AddressTypeDomain_019f6c2b-a781-7b5f-a5a7-19b1968484cc" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AddressTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_EntityAddressesAddressTypeAxis_019f6c2b-a781-749c-8d4d-52f2acb6bcc5" xlink:to="loc_dei_AddressTypeDomain_019f6c2b-a781-7b5f-a5a7-19b1968484cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_FormerAddressMember_019f6c2b-a781-73d2-ae4e-17117b2c48b5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_FormerAddressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_AddressTypeDomain_019f6c2b-a781-7b5f-a5a7-19b1968484cc" xlink:to="loc_dei_FormerAddressMember_019f6c2b-a781-73d2-ae4e-17117b2c48b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019f6c2b-a781-72dc-9e55-945daf8b0faa" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_DocumentType_019f6c2b-a781-72dc-9e55-945daf8b0faa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019f6c2b-a781-7c6d-9812-cce26f5e1e0a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_DocumentPeriodEndDate_019f6c2b-a781-7c6d-9812-cce26f5e1e0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019f6c2b-a781-77c9-a145-0fb4e7140887" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityFileNumber_019f6c2b-a781-77c9-a145-0fb4e7140887" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019f6c2b-a781-766c-90f5-f27dac6ef43f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityRegistrantName_019f6c2b-a781-766c-90f5-f27dac6ef43f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019f6c2b-a781-7d4d-9239-81cf37115d02" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityTaxIdentificationNumber_019f6c2b-a781-7d4d-9239-81cf37115d02" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019f6c2b-a781-7f88-a723-13ff76f0f59c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019f6c2b-a781-7f88-a723-13ff76f0f59c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019f6c2b-a781-70d9-87b8-ea03f24eee53" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityAddressAddressLine1_019f6c2b-a781-70d9-87b8-ea03f24eee53" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019f6c2b-a781-7dcf-8ff6-4ffe4fb73198" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityAddressAddressLine2_019f6c2b-a781-7dcf-8ff6-4ffe4fb73198" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019f6c2b-a781-73c0-87e6-3bca45bdc8e1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityAddressCityOrTown_019f6c2b-a781-73c0-87e6-3bca45bdc8e1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019f6c2b-a781-7bb9-b71d-ec04e61e8998" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityAddressStateOrProvince_019f6c2b-a781-7bb9-b71d-ec04e61e8998" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019f6c2b-a781-788f-baff-b9799e94b9f4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityAddressPostalZipCode_019f6c2b-a781-788f-baff-b9799e94b9f4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019f6c2b-a781-7bec-b82a-2fbceea593ab" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_CityAreaCode_019f6c2b-a781-7bec-b82a-2fbceea593ab" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019f6c2b-a781-7a8b-834d-0381b30944d2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_LocalPhoneNumber_019f6c2b-a781-7a8b-834d-0381b30944d2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019f6c2b-a781-7871-965b-41c2f6d72007" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_WrittenCommunications_019f6c2b-a781-7871-965b-41c2f6d72007" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019f6c2b-a781-774a-9ad5-e6e53b02803f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_SolicitingMaterial_019f6c2b-a781-774a-9ad5-e6e53b02803f" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019f6c2b-a781-754f-b465-bea1678c9635" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_PreCommencementTenderOffer_019f6c2b-a781-754f-b465-bea1678c9635" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019f6c2b-a781-7866-9ece-49f5477c1455" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019f6c2b-a781-7866-9ece-49f5477c1455" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_019f6c2b-a781-79b3-a978-486e889dff26" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityExTransitionPeriod_019f6c2b-a781-79b3-a978-486e889dff26" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019f6c2b-a781-72a3-8497-cfb0d14ca849" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityEmergingGrowthCompany_019f6c2b-a781-72a3-8497-cfb0d14ca849" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019f6c2b-a781-7c97-a7b0-8c13e5d5a2ca" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_EntityCentralIndexKey_019f6c2b-a781-7c97-a7b0-8c13e5d5a2ca" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019f6c2b-a781-7360-9ef8-94da9223e2a6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f6c2b-a781-7434-9012-f4988a1fc236" xlink:to="loc_dei_AmendmentFlag_019f6c2b-a781-7360-9ef8-94da9223e2a6" xlink:type="arc" order="20"/>
  </link:definitionLink>
</link:linkbase>
