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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:595961a6-c05b-4518-b533-5ab34c8fd55a,g:fd842f59-5a9b-438b-8bfd-0f565ff46c32-->
<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://www.neuropace.com/role/StatementsStockholdersEquity" xlink:type="simple" xlink:href="npce-20251231.xsd#StatementsStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StatementsStockholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ffcf2553-e1da-4913-95d2-e4a327283e0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_351fecc3-7a1d-4be0-8c19-edb0c54db43c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ffcf2553-e1da-4913-95d2-e4a327283e0c" xlink:to="loc_us-gaap_StatementTable_351fecc3-7a1d-4be0-8c19-edb0c54db43c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_bea0d830-3479-4aea-9515-30846c555896" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_351fecc3-7a1d-4be0-8c19-edb0c54db43c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_bea0d830-3479-4aea-9515-30846c555896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_bea0d830-3479-4aea-9515-30846c555896_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_bea0d830-3479-4aea-9515-30846c555896" xlink:to="loc_us-gaap_EquityComponentDomain_bea0d830-3479-4aea-9515-30846c555896_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9fedb8db-e9da-4b57-925e-f2ab27adef86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_bea0d830-3479-4aea-9515-30846c555896" xlink:to="loc_us-gaap_EquityComponentDomain_9fedb8db-e9da-4b57-925e-f2ab27adef86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_cefb43d8-8732-46fa-bc20-35b4c934913e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9fedb8db-e9da-4b57-925e-f2ab27adef86" xlink:to="loc_us-gaap_CommonStockMember_cefb43d8-8732-46fa-bc20-35b4c934913e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_7f5e4197-1be2-4305-8a2d-7000d4a3b08d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9fedb8db-e9da-4b57-925e-f2ab27adef86" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_7f5e4197-1be2-4305-8a2d-7000d4a3b08d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_8d4f066d-9c80-4db3-ac24-2828c1a40cab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_9fedb8db-e9da-4b57-925e-f2ab27adef86" xlink:to="loc_us-gaap_RetainedEarningsMember_8d4f066d-9c80-4db3-ac24-2828c1a40cab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fc9-0626-74b3-8908-9a02b2d0b28c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_351fecc3-7a1d-4be0-8c19-edb0c54db43c" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fc9-0626-74b3-8908-9a02b2d0b28c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fc9-0626-74b3-8908-9a02b2d0b28c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fc9-0626-74b3-8908-9a02b2d0b28c" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fc9-0626-74b3-8908-9a02b2d0b28c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fc9-0626-7469-9999-70cb1e7f8f00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fc9-0626-74b3-8908-9a02b2d0b28c" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fc9-0626-7469-9999-70cb1e7f8f00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_AtTheMarketEquityOfferingMember_019b2fd0-d069-77f8-b3ed-311792e581a0" xlink:href="npce-20251231.xsd#npce_AtTheMarketEquityOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fc9-0626-7469-9999-70cb1e7f8f00" xlink:to="loc_npce_AtTheMarketEquityOfferingMember_019b2fd0-d069-77f8-b3ed-311792e581a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_FollowOnOfferingMember_019b2fc9-0626-74fb-8186-a2690ecc8a33" xlink:href="npce-20251231.xsd#npce_FollowOnOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fc9-0626-7469-9999-70cb1e7f8f00" xlink:to="loc_npce_FollowOnOfferingMember_019b2fc9-0626-74fb-8186-a2690ecc8a33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ffcf2553-e1da-4913-95d2-e4a327283e0c" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_3ae954f3-58e0-4d05-9784-b5b0b356ecfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_3ae954f3-58e0-4d05-9784-b5b0b356ecfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_ac7b0529-eef8-4d98-b58a-5edc825b94b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockholdersEquity_ac7b0529-eef8-4d98-b58a-5edc825b94b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_60fa9f41-1ab6-4975-a474-03c8f7cced09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_NetIncomeLoss_60fa9f41-1ab6-4975-a474-03c8f7cced09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_362ded3e-02f7-48ae-9a02-99f715bdd7be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_362ded3e-02f7-48ae-9a02-99f715bdd7be" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_367fad9c-ed46-43a8-a9af-de25700d8eb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_367fad9c-ed46-43a8-a9af-de25700d8eb2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_2066f2f3-2a1d-409f-959d-ccba391646d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_2066f2f3-2a1d-409f-959d-ccba391646d7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019b2fc9-9c14-736e-bdf1-652eee929ed0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019b2fc9-9c14-736e-bdf1-652eee929ed0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_bbf395c7-2ce4-41b1-b004-511f1c8b118d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_bbf395c7-2ce4-41b1-b004-511f1c8b118d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_153ff926-ba40-4400-9ea6-5b22b7f797b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_153ff926-ba40-4400-9ea6-5b22b7f797b3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_cfa800e0-690f-4e30-9f2e-9f93fdc00001" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_cfa800e0-690f-4e30-9f2e-9f93fdc00001" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_8d9d63fc-b69f-42cc-9fae-37c3919cccb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_8d9d63fc-b69f-42cc-9fae-37c3919cccb6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_da4fe08c-5de0-4114-af2b-0b194f417163" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_da4fe08c-5de0-4114-af2b-0b194f417163" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_47462251-7ec3-4d87-8ba8-b6a66eca592b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_47462251-7ec3-4d87-8ba8-b6a66eca592b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_a2697c48-4271-4efe-9e6c-db7c86a68e69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_a2697c48-4271-4efe-9e6c-db7c86a68e69" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_3bd6feaa-7cf0-4536-856e-9ea94f62708f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_3bd6feaa-7cf0-4536-856e-9ea94f62708f" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_AdjustmentsToAdditionalPaidInCapitalChangeInEarlyExerciseLiability_6df2f5e9-c3eb-43b6-889f-ca5d41d7465f" xlink:href="npce-20251231.xsd#npce_AdjustmentsToAdditionalPaidInCapitalChangeInEarlyExerciseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_npce_AdjustmentsToAdditionalPaidInCapitalChangeInEarlyExerciseLiability_6df2f5e9-c3eb-43b6-889f-ca5d41d7465f" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_4cf7dffc-9926-4da5-9d73-fff00d647506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_e9b8cc33-8610-47f5-ae5f-c6bb9ce590ef" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_4cf7dffc-9926-4da5-9d73-fff00d647506" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_0f6a4c72-76cd-4a8d-bc79-9baac964270d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_b95dbfe9-1ef9-44bd-81a6-7ef989c91060" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StatementsofStockholdersEquityParenthetical" xlink:type="simple" xlink:href="npce-20251231.xsd#StatementsofStockholdersEquityParenthetical"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StatementsofStockholdersEquityParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c8bff-5eb5-76fb-9a97-36f9bdf30a10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c8bfd-afa3-73eb-b28d-aea9b4c8be7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c8bff-5eb5-76fb-9a97-36f9bdf30a10" xlink:to="loc_us-gaap_StatementTable_019c8bfd-afa3-73eb-b28d-aea9b4c8be7e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_019c8bfd-fedb-7a74-9a16-d73e3217cd52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c8bfd-afa3-73eb-b28d-aea9b4c8be7e" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_019c8bfd-fedb-7a74-9a16-d73e3217cd52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c8bfd-fedb-7a74-9a16-d73e3217cd52_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019c8bfd-fedb-7a74-9a16-d73e3217cd52" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c8bfd-fedb-7a74-9a16-d73e3217cd52_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c8bfe-2197-7293-b485-75d0ea22c85a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019c8bfd-fedb-7a74-9a16-d73e3217cd52" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c8bfe-2197-7293-b485-75d0ea22c85a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_AtTheMarketEquityOfferingMember_019c8bfe-d4fa-7bfd-a63d-2fe7b52abd65" xlink:href="npce-20251231.xsd#npce_AtTheMarketEquityOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c8bfe-2197-7293-b485-75d0ea22c85a" xlink:to="loc_npce_AtTheMarketEquityOfferingMember_019c8bfe-d4fa-7bfd-a63d-2fe7b52abd65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_FollowOnOfferingMember_019c8bfe-77a0-7286-9cf7-f8a7893397bd" xlink:href="npce-20251231.xsd#npce_FollowOnOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c8bfe-2197-7293-b485-75d0ea22c85a" xlink:to="loc_npce_FollowOnOfferingMember_019c8bfe-77a0-7286-9cf7-f8a7893397bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_2c3fe081-cb90-47b5-acb4-6b4c1f63b84f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c8bff-5eb5-76fb-9a97-36f9bdf30a10" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_2c3fe081-cb90-47b5-acb4-6b4c1f63b84f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StatementsofCashFlows" xlink:type="simple" xlink:href="npce-20251231.xsd#StatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019bb1e9-09e7-712a-a686-3fad6f14b0b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_StatementTable_019bb1e9-09e7-712a-a686-3fad6f14b0b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_019bb1e9-09e7-7481-b94b-48182d39c627" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019bb1e9-09e7-712a-a686-3fad6f14b0b1" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_019bb1e9-09e7-7481-b94b-48182d39c627" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019bb1e9-09e7-7481-b94b-48182d39c627_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019bb1e9-09e7-7481-b94b-48182d39c627" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019bb1e9-09e7-7481-b94b-48182d39c627_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019bb1e9-09e7-7003-898d-af4cb0def73d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019bb1e9-09e7-7481-b94b-48182d39c627" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019bb1e9-09e7-7003-898d-af4cb0def73d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_FollowOnOfferingMember_019bb1e9-09e7-7e5e-8f2c-5bcb7456ef97" xlink:href="npce-20251231.xsd#npce_FollowOnOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019bb1e9-09e7-7003-898d-af4cb0def73d" xlink:to="loc_npce_FollowOnOfferingMember_019bb1e9-09e7-7e5e-8f2c-5bcb7456ef97" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_AtTheMarketEquityOfferingMember_019bb1e9-09e7-7ff7-91d0-7d71d38eab8a" xlink:href="npce-20251231.xsd#npce_AtTheMarketEquityOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019bb1e9-09e7-7003-898d-af4cb0def73d" xlink:to="loc_npce_AtTheMarketEquityOfferingMember_019bb1e9-09e7-7ff7-91d0-7d71d38eab8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_5915d5bc-ede2-4108-a2ea-7955160c8b1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_5915d5bc-ede2-4108-a2ea-7955160c8b1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_d77ba2e3-8b36-46f8-9c00-f521fefd3c4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_5915d5bc-ede2-4108-a2ea-7955160c8b1e" xlink:to="loc_us-gaap_NetIncomeLoss_d77ba2e3-8b36-46f8-9c00-f521fefd3c4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_5915d5bc-ede2-4108-a2ea-7955160c8b1e" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_1abbb66a-da0e-44b5-b1ce-f3f802f96132" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_ShareBasedCompensation_1abbb66a-da0e-44b5-b1ce-f3f802f96132" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_938ad42c-ffac-4ead-b7fe-368163652eeb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_Depreciation_938ad42c-ffac-4ead-b7fe-368163652eeb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_aa5b6cce-0d34-475d-9053-7372cd76adc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_aa5b6cce-0d34-475d-9053-7372cd76adc3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_IncreaseDecreaseInNonCashInterestExpense_7dcf348c-4a21-42c9-bea6-388c61e5482a" xlink:href="npce-20251231.xsd#npce_IncreaseDecreaseInNonCashInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_npce_IncreaseDecreaseInNonCashInterestExpense_7dcf348c-4a21-42c9-bea6-388c61e5482a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaidInKindInterest_7f14c0a8-1848-48fc-a2da-6952ad742e93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaidInKindInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_PaidInKindInterest_7f14c0a8-1848-48fc-a2da-6952ad742e93" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019bb1ce-95ca-79ac-89aa-7b9b0b233d85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019bb1ce-95ca-79ac-89aa-7b9b0b233d85" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_2f75d34a-7c51-47d5-8abd-a704f190ed62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_2f75d34a-7c51-47d5-8abd-a704f190ed62" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfInvestments_f91de8c0-4772-4c94-9d5b-7053cbe1119e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_GainLossOnSaleOfInvestments_f91de8c0-4772-4c94-9d5b-7053cbe1119e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWriteDown_12a467bb-f712-48cd-9822-7f731240c724" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_InventoryWriteDown_12a467bb-f712-48cd-9822-7f731240c724" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019bb1cf-6c31-7f37-99aa-7340e5616465" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019bb1cf-6c31-7f37-99aa-7340e5616465" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_9b85b0ff-6f5a-4b11-b59c-c4ea67248cf9" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_0023decf-ef48-4057-8223-038b4388eaa7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_0023decf-ef48-4057-8223-038b4388eaa7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_08964b1f-0dcb-45f3-8bb8-1ea90d35bb40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_08964b1f-0dcb-45f3-8bb8-1ea90d35bb40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_a9e60edc-7505-41f2-bbca-1903c5b4cfaa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_a9e60edc-7505-41f2-bbca-1903c5b4cfaa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_08ac2179-0b83-4698-b92c-410f58367953" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_08ac2179-0b83-4698-b92c-410f58367953" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_85d02cbc-934d-43d7-ad4d-3368b6bee279" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_85d02cbc-934d-43d7-ad4d-3368b6bee279" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_cd5b632f-289b-455c-a80a-3c975a29e876" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_cd5b632f-289b-455c-a80a-3c975a29e876" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingLeaseLiability_fb5cbe76-fa1b-41ea-9a12-93e21605087b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_e7db1d84-aa15-43ab-804f-8ee2137288f6" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingLeaseLiability_fb5cbe76-fa1b-41ea-9a12-93e21605087b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_18019250-362c-4900-a6dd-8ba41fb64a20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_5915d5bc-ede2-4108-a2ea-7955160c8b1e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_18019250-362c-4900-a6dd-8ba41fb64a20" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_1a12895b-128a-45a6-abd5-f0b76e1525eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_1a12895b-128a-45a6-abd5-f0b76e1525eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019010c2-e46e-41f1-aba1-c61a1c2dd0e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_1a12895b-128a-45a6-abd5-f0b76e1525eb" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019010c2-e46e-41f1-aba1-c61a1c2dd0e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfShortTermInvestments_6f92c80e-c8c7-4ced-8249-ccd55a484b48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_1a12895b-128a-45a6-abd5-f0b76e1525eb" xlink:to="loc_us-gaap_ProceedsFromSaleOfShortTermInvestments_6f92c80e-c8c7-4ced-8249-ccd55a484b48" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_d01f27be-1f56-41ee-bd94-b2752fcbd204" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_1a12895b-128a-45a6-abd5-f0b76e1525eb" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_d01f27be-1f56-41ee-bd94-b2752fcbd204" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019bb1d0-7e79-7d30-979d-4aa37d01eaee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019bb1d0-7e79-7d30-979d-4aa37d01eaee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019bb1d0-7e79-77d6-959e-c3779263cd86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_019bb1d0-7e79-77d6-959e-c3779263cd86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_1f94dc14-d826-45be-a423-4a7457d942aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_1f94dc14-d826-45be-a423-4a7457d942aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_ae87009b-d342-467e-a1b7-cd72eaf63965" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_ae87009b-d342-467e-a1b7-cd72eaf63965" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_96bf8c1f-3e5b-44e1-a1a9-7ecc3fb1a518" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceInitialPublicOffering"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_96bf8c1f-3e5b-44e1-a1a9-7ecc3fb1a518" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDebtNetOfIssuanceCosts_019bb1d0-c787-7f3a-b4b9-8d576e086416" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDebtNetOfIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_ProceedsFromDebtNetOfIssuanceCosts_019bb1d0-c787-7f3a-b4b9-8d576e086416" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019bb1d0-c787-7fa2-8586-e3b1e4fb8259" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019bb1d0-c787-7fa2-8586-e3b1e4fb8259" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d3495211-ad15-4458-a7e7-256095cab906" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_c9d7256e-cb90-4a4f-bc98-5b025c639d49" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d3495211-ad15-4458-a7e7-256095cab906" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_edcebb64-e11a-4e16-bb8a-e9d1255258fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_edcebb64-e11a-4e16-bb8a-e9d1255258fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_cc7fc9f2-b52b-4bf0-ab8c-9f4170fd8915" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_cc7fc9f2-b52b-4bf0-ab8c-9f4170fd8915" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_96052db7-e790-4d82-9d22-ddd167c81d17" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_98819bcd-b2aa-4a34-af61-283b899a85c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_98819bcd-b2aa-4a34-af61-283b899a85c8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_34340176-60c5-463c-930f-fd3fb8392cc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_98819bcd-b2aa-4a34-af61-283b899a85c8" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_34340176-60c5-463c-930f-fd3fb8392cc3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_dca52c3a-3dce-4a1e-8370-cffc31cd54bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_98819bcd-b2aa-4a34-af61-283b899a85c8" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_dca52c3a-3dce-4a1e-8370-cffc31cd54bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_dc9d6d29-8618-44cd-bbab-01e6cfe982a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_1482fd24-260a-40c8-bf18-a32894f6d140" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_1482fd24-260a-40c8-bf18-a32894f6d140" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_af8fcac0-e76c-4986-b391-eaa2096edec0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_1482fd24-260a-40c8-bf18-a32894f6d140" xlink:to="loc_us-gaap_InterestPaidNet_af8fcac0-e76c-4986-b391-eaa2096edec0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_86b08f14-5ede-4cc0-a94f-d0b8395feb46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019bb1e9-d743-7ea6-beb0-3c1700a8134e" xlink:to="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_86b08f14-5ede-4cc0-a94f-d0b8395feb46" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DeferredOfferingCostsOffsetAgainstAdditionalPaidInCapital_a26d10ec-8334-421f-ae94-8d8eebc0ea19" xlink:href="npce-20251231.xsd#npce_DeferredOfferingCostsOffsetAgainstAdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_86b08f14-5ede-4cc0-a94f-d0b8395feb46" xlink:to="loc_npce_DeferredOfferingCostsOffsetAgainstAdditionalPaidInCapital_a26d10ec-8334-421f-ae94-8d8eebc0ea19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_fce9afc2-a9b0-4446-9d5b-e7f0c92c7d2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_86b08f14-5ede-4cc0-a94f-d0b8395feb46" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_fce9afc2-a9b0-4446-9d5b-e7f0c92c7d2c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_IncreaseDecreaseInAccruedLiabilitiesEarlyExerciseOfOptions_514c49e7-6b31-4822-bb34-01a6d0f69f02" xlink:href="npce-20251231.xsd#npce_IncreaseDecreaseInAccruedLiabilitiesEarlyExerciseOfOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_86b08f14-5ede-4cc0-a94f-d0b8395feb46" xlink:to="loc_npce_IncreaseDecreaseInAccruedLiabilitiesEarlyExerciseOfOptions_514c49e7-6b31-4822-bb34-01a6d0f69f02" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/TheCompanyDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#TheCompanyDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/TheCompanyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_019b2fdf-5609-7d93-af83-09fcf97cee23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_019b2fdf-5609-7d93-af83-09fcf97cee23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fdf-5609-7a61-9356-1f795d1cca83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_019b2fdf-5609-7d93-af83-09fcf97cee23" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fdf-5609-7a61-9356-1f795d1cca83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7a61-9356-1f795d1cca83_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fdf-5609-7a61-9356-1f795d1cca83" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7a61-9356-1f795d1cca83_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7e50-b21f-3b4ce6f73e61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019b2fdf-5609-7a61-9356-1f795d1cca83" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7e50-b21f-3b4ce6f73e61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_AtTheMarketEquityOfferingMember_019b2fdf-5609-76e1-9013-6998490e7ec7" xlink:href="npce-20251231.xsd#npce_AtTheMarketEquityOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7e50-b21f-3b4ce6f73e61" xlink:to="loc_npce_AtTheMarketEquityOfferingMember_019b2fdf-5609-76e1-9013-6998490e7ec7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_FollowOnOfferingMember_019b2fdf-5609-7d22-93ef-83bf11ccde86" xlink:href="npce-20251231.xsd#npce_FollowOnOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7e50-b21f-3b4ce6f73e61" xlink:to="loc_npce_FollowOnOfferingMember_019b2fdf-5609-7d22-93ef-83bf11ccde86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OverAllotmentOptionMember_019b2fdf-5609-75ea-b366-954e030e64e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OverAllotmentOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019b2fdf-5609-7e50-b21f-3b4ce6f73e61" xlink:to="loc_us-gaap_OverAllotmentOptionMember_019b2fdf-5609-75ea-b366-954e030e64e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019b2fdf-5609-7eef-a8ce-9c9d66676bfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_019b2fdf-5609-7d93-af83-09fcf97cee23" xlink:to="loc_us-gaap_DebtInstrumentAxis_019b2fdf-5609-7eef-a8ce-9c9d66676bfe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019b2fdf-5609-7eef-a8ce-9c9d66676bfe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019b2fdf-5609-7eef-a8ce-9c9d66676bfe" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019b2fdf-5609-7eef-a8ce-9c9d66676bfe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019b2fdf-5609-7377-9f73-d2836e2e3688" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019b2fdf-5609-7eef-a8ce-9c9d66676bfe" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019b2fdf-5609-7377-9f73-d2836e2e3688" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_MidCapAgreementMember_019b2fdf-5609-72bc-96b8-7add16b5ab60" xlink:href="npce-20251231.xsd#npce_MidCapAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019b2fdf-5609-7377-9f73-d2836e2e3688" xlink:to="loc_npce_MidCapAgreementMember_019b2fdf-5609-72bc-96b8-7add16b5ab60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019b2fdf-5609-73aa-9dec-b99dc2f3150c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_019b2fdf-5609-7d93-af83-09fcf97cee23" xlink:to="loc_srt_ProductOrServiceAxis_019b2fdf-5609-73aa-9dec-b99dc2f3150c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019b2fdf-5609-73aa-9dec-b99dc2f3150c_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019b2fdf-5609-73aa-9dec-b99dc2f3150c" xlink:to="loc_srt_ProductsAndServicesDomain_019b2fdf-5609-73aa-9dec-b99dc2f3150c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019b2fdf-5609-7d7c-96e3-82041a06fcfc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019b2fdf-5609-73aa-9dec-b99dc2f3150c" xlink:to="loc_srt_ProductsAndServicesDomain_019b2fdf-5609-7d7c-96e3-82041a06fcfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_RNSSystemMember_019b2fdf-5609-7b2a-a240-02e3abfb6c93" xlink:href="npce-20251231.xsd#npce_RNSSystemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019b2fdf-5609-7d7c-96e3-82041a06fcfc" xlink:to="loc_npce_RNSSystemMember_019b2fdf-5609-7b2a-a240-02e3abfb6c93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019b2fdf-5609-79a7-a333-defd6d1eef74" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_019b2fdf-5609-7d93-af83-09fcf97cee23" xlink:to="loc_srt_StatementScenarioAxis_019b2fdf-5609-79a7-a333-defd6d1eef74" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019b2fdf-5609-79a7-a333-defd6d1eef74_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019b2fdf-5609-79a7-a333-defd6d1eef74" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019b2fdf-5609-79a7-a333-defd6d1eef74_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019b2fdf-5609-7f4c-8c8d-e59492175567" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019b2fdf-5609-79a7-a333-defd6d1eef74" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019b2fdf-5609-7f4c-8c8d-e59492175567" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_019b2fdf-5609-7de3-a846-02589e21463e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019b2fdf-5609-7f4c-8c8d-e59492175567" xlink:to="loc_srt_ScenarioForecastMember_019b2fdf-5609-7de3-a846-02589e21463e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfPreferredStockPreferenceStockAndWarrants_019b2fdf-5609-7742-8336-ccca92692b65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfPreferredStockPreferenceStockAndWarrants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfPreferredStockPreferenceStockAndWarrants_019b2fdf-5609-7742-8336-ccca92692b65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_019b2fdf-5609-7698-82fd-ecda65ba6002" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_019b2fdf-5609-7698-82fd-ecda65ba6002" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_PercentageOfSharesOfCommonStockSoldUnderTheSalesAgreement_019b2fdf-5609-79ed-a0b1-93d485041286" xlink:href="npce-20251231.xsd#npce_PercentageOfSharesOfCommonStockSoldUnderTheSalesAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_PercentageOfSharesOfCommonStockSoldUnderTheSalesAgreement_019b2fdf-5609-79ed-a0b1-93d485041286" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_019b2fdf-5609-7924-9f12-af078f57d610" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_019b2fdf-5609-7924-9f12-af078f57d610" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019b2fdf-5609-768f-a690-fe0c956e5458" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_019b2fdf-5609-768f-a690-fe0c956e5458" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ProceedsFromIssuanceOfCommonStockNetOfSalesCommissionsAndOfferingCosts_019b2fdf-5609-7878-8885-511d4684967d" xlink:href="npce-20251231.xsd#npce_ProceedsFromIssuanceOfCommonStockNetOfSalesCommissionsAndOfferingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_ProceedsFromIssuanceOfCommonStockNetOfSalesCommissionsAndOfferingCosts_019b2fdf-5609-7878-8885-511d4684967d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_EquityOfferingAgreementRemainingAmountAvailable_019b2fdf-5609-7303-858a-2f7d679ed64e" xlink:href="npce-20251231.xsd#npce_EquityOfferingAgreementRemainingAmountAvailable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_EquityOfferingAgreementRemainingAmountAvailable_019b2fdf-5609-7303-858a-2f7d679ed64e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_019b2fdf-5609-7125-aed2-d98c18ac4ab9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_019b2fdf-5609-7125-aed2-d98c18ac4ab9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_019b2fdf-5609-734f-890c-c7fb5ed91453" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_019b2fdf-5609-734f-890c-c7fb5ed91453" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019b2fdf-5609-721c-8673-a7f986554ad5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019b2fdf-5609-721c-8673-a7f986554ad5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019b2fdf-5609-74ec-89dd-45a2e4d0caf0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019b2fdf-5609-74ec-89dd-45a2e4d0caf0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019b2fdf-5609-7469-8608-de1953ca6859" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019b2fdf-5609-7469-8608-de1953ca6859" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019b2fdf-5609-794b-96f3-ffc8b52bbb3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019b2fdf-5609-794b-96f3-ffc8b52bbb3e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019b2fdf-5609-7754-b5fc-8fd3ce72afcb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019b2fdf-5609-7754-b5fc-8fd3ce72afcb" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_019b2fdf-5609-776e-932c-257172846575" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_019b2fdf-5609-776e-932c-257172846575" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantLiquidityThresholdAmountInNextTwoYears_019b2fdf-5609-7257-acf3-c1488459f02c" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantLiquidityThresholdAmountInNextTwoYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantLiquidityThresholdAmountInNextTwoYears_019b2fdf-5609-7257-acf3-c1488459f02c" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantLiquidityThresholdAmountThereafter_019b2fdf-5609-7eea-a950-d1bfd7fbf84d" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantLiquidityThresholdAmountThereafter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantLiquidityThresholdAmountThereafter_019b2fdf-5609-7eea-a950-d1bfd7fbf84d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantMinimumAnnualNetRevenueInNextTwelveMonths_019b2fdf-5609-7607-aba7-bfa21fa83c75" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantMinimumAnnualNetRevenueInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantMinimumAnnualNetRevenueInNextTwelveMonths_019b2fdf-5609-7607-aba7-bfa21fa83c75" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantMinimumLiquidityIfRevenueThresholdMet_019b2fdf-5609-74f4-a40e-fdeee1fe504a" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantMinimumLiquidityIfRevenueThresholdMet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantMinimumLiquidityIfRevenueThresholdMet_019b2fdf-5609-74f4-a40e-fdeee1fe504a" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantMaximumAnnualNetRevenue_019b2fdf-5609-7078-ac95-7f0f846fe5b5" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantMaximumAnnualNetRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantMaximumAnnualNetRevenue_019b2fdf-5609-7078-ac95-7f0f846fe5b5" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantAnnualNetRevenue_019b2fdf-5609-7beb-b14a-a703f5e786ac" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantAnnualNetRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantAnnualNetRevenue_019b2fdf-5609-7beb-b14a-a703f5e786ac" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantAnnualMinimumNetRevenue_019b2fdf-5609-71c1-9ce4-4f8ed5680593" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantAnnualMinimumNetRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantAnnualMinimumNetRevenue_019b2fdf-5609-71c1-9ce4-4f8ed5680593" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantMinimumLiquidityThresholdBalance_019b2fdf-5609-7792-b75a-05edb4e6071f" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantMinimumLiquidityThresholdBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019b2fdf-5609-70a1-8b98-b4c12bb3ca78" xlink:to="loc_npce_DebtInstrumentCovenantMinimumLiquidityThresholdBalance_019b2fdf-5609-7792-b75a-05edb4e6071f" xlink:type="arc" order="22"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#SummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_a41f0512-e796-4dfb-a78f-c44a09fca292" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_a41f0512-e796-4dfb-a78f-c44a09fca292" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019b2ffb-1434-7ce3-8e24-910267cfbcc5" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_a41f0512-e796-4dfb-a78f-c44a09fca292" xlink:to="loc_srt_MajorCustomersAxis_019b2ffb-1434-7ce3-8e24-910267cfbcc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019b2ffb-1434-7ce3-8e24-910267cfbcc5_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019b2ffb-1434-7ce3-8e24-910267cfbcc5" xlink:to="loc_srt_NameOfMajorCustomerDomain_019b2ffb-1434-7ce3-8e24-910267cfbcc5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019b2ffb-1434-7b6b-a312-9e96ab41ed7b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019b2ffb-1434-7ce3-8e24-910267cfbcc5" xlink:to="loc_srt_NameOfMajorCustomerDomain_019b2ffb-1434-7b6b-a312-9e96ab41ed7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_RapportMember_019b2ffb-1434-7390-8477-38bbc7d536b9" xlink:href="npce-20251231.xsd#npce_RapportMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019b2ffb-1434-7b6b-a312-9e96ab41ed7b" xlink:to="loc_npce_RapportMember_019b2ffb-1434-7390-8477-38bbc7d536b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019b2ffb-f9f7-7a09-88f0-dd974a7bfdf3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_a41f0512-e796-4dfb-a78f-c44a09fca292" xlink:to="loc_srt_RangeAxis_019b2ffb-f9f7-7a09-88f0-dd974a7bfdf3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019b2ffb-f9f7-7a09-88f0-dd974a7bfdf3_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019b2ffb-f9f7-7a09-88f0-dd974a7bfdf3" xlink:to="loc_srt_RangeMember_019b2ffb-f9f7-7a09-88f0-dd974a7bfdf3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019b2ffb-f9f7-7c98-a4d0-badff64b310e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019b2ffb-f9f7-7a09-88f0-dd974a7bfdf3" xlink:to="loc_srt_RangeMember_019b2ffb-f9f7-7c98-a4d0-badff64b310e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019b2ffb-f9f7-7e19-9d3b-0fd37b08d5a2" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019b2ffb-f9f7-7c98-a4d0-badff64b310e" xlink:to="loc_srt_MinimumMember_019b2ffb-f9f7-7e19-9d3b-0fd37b08d5a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019b2ffb-f9f7-7b32-a6ff-1c68b6143364" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019b2ffb-f9f7-7c98-a4d0-badff64b310e" xlink:to="loc_srt_MaximumMember_019b2ffb-f9f7-7b32-a6ff-1c68b6143364" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_019b2ffc-6115-7ee6-9889-c81c245e1a53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_a41f0512-e796-4dfb-a78f-c44a09fca292" xlink:to="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_019b2ffc-6115-7ee6-9889-c81c245e1a53" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_019b2ffc-6115-7ee6-9889-c81c245e1a53_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_019b2ffc-6115-7ee6-9889-c81c245e1a53" xlink:to="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_019b2ffc-6115-7ee6-9889-c81c245e1a53_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_019b2ffc-6115-777d-a972-515cc7308cf0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_019b2ffc-6115-7ee6-9889-c81c245e1a53" xlink:to="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_019b2ffc-6115-777d-a972-515cc7308cf0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalFundingAgreementTermsMember_019b2ffc-6115-7723-b6c6-7297a3197fa2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalFundingAgreementTermsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_019b2ffc-6115-777d-a972-515cc7308cf0" xlink:to="loc_us-gaap_AdditionalFundingAgreementTermsMember_019b2ffc-6115-7723-b6c6-7297a3197fa2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_RevenueContractualPeriod_019b2ffb-1434-798d-8c27-ec977b4c05a0" xlink:href="npce-20251231.xsd#npce_RevenueContractualPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_RevenueContractualPeriod_019b2ffb-1434-798d-8c27-ec977b4c05a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019b2ffb-1434-7854-9b22-c81368f5c928" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019b2ffb-1434-7854-9b22-c81368f5c928" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerReceivableAfterAllowanceForCreditLossCurrent_019b2ffb-4b75-7448-a6f1-5e8bee75d1d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerReceivableAfterAllowanceForCreditLossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ContractWithCustomerReceivableAfterAllowanceForCreditLossCurrent_019b2ffb-4b75-7448-a6f1-5e8bee75d1d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019b2ffb-4b75-7d03-8e40-0859cc6d08d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_019b2ffb-4b75-7d03-8e40-0859cc6d08d8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019b2ffb-4b75-7425-8001-33836ed49bc6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_019b2ffb-4b75-7425-8001-33836ed49bc6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019b2ffb-4b75-7455-9176-d6a169562c1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019b2ffb-4b75-7455-9176-d6a169562c1e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGross_019b2ffb-9adb-73e4-8f57-4e056522c58d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_AccountsReceivableGross_019b2ffb-9adb-73e4-8f57-4e056522c58d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWriteDown_019b2ffb-d642-7aba-8d07-2014345ca90e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_InventoryWriteDown_019b2ffb-d642-7aba-8d07-2014345ca90e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_019b2ffb-f9f7-7ddb-b158-6d16eabf9471" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_019b2ffb-f9f7-7ddb-b158-6d16eabf9471" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_019b2ffc-1315-7581-96a0-18e95ed3f9ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ImpairmentOfLongLivedAssetsHeldForUse"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_019b2ffc-1315-7581-96a0-18e95ed3f9ac" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DeferredOfferingCostsOffsetAgainstAdditionalPaidInCapital_019c462b-6396-7617-9841-b8d33406c809" xlink:href="npce-20251231.xsd#npce_DeferredOfferingCostsOffsetAgainstAdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_DeferredOfferingCostsOffsetAgainstAdditionalPaidInCapital_019c462b-6396-7617-9841-b8d33406c809" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCosts_019c462a-eb10-759d-bc86-3f2859978d8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_DeferredCosts_019c462a-eb10-759d-bc86-3f2859978d8d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentTerm_019b2ffc-6115-79ca-a1c9-75ed1481b79c" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentTerm_019b2ffc-6115-79ca-a1c9-75ed1481b79c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentTotalEstimatedCost_019b2ffc-6115-7977-94d9-26d71db3031e" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentTotalEstimatedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentTotalEstimatedCost_019b2ffc-6115-7977-94d9-26d71db3031e" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentEstimatedCostForSubawards_019b2ffc-6115-77ef-a9a7-f811ce1e1d7c" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentEstimatedCostForSubawards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentEstimatedCostForSubawards_019b2ffc-6115-77ef-a9a7-f811ce1e1d7c" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovedFundingYear1_019b2ffc-6115-71d8-9fbc-ff9ef658c80b" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovedFundingYear1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovedFundingYear1_019b2ffc-6115-71d8-9fbc-ff9ef658c80b" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovedFundingSubawardsYear1_019b2ffc-6115-7c43-8193-fd6b4260b2c5" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovedFundingSubawardsYear1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovedFundingSubawardsYear1_019b2ffc-6115-7c43-8193-fd6b4260b2c5" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingYear2_019b2ffc-6115-77a2-9292-1d152ecfc435" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingYear2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingYear2_019b2ffc-6115-77a2-9292-1d152ecfc435" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingSubawardsYear2_019b2ffc-6115-72ce-9831-49daf5aa3002" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingSubawardsYear2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingSubawardsYear2_019b2ffc-6115-72ce-9831-49daf5aa3002" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingYear5_019b2ffc-6115-7d7f-8ca7-c260468c7f9b" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingYear5"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingYear5_019b2ffc-6115-7d7f-8ca7-c260468c7f9b" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingSubawardsYear5_019b2ffc-6115-78b4-9f4c-4b291485762e" xlink:href="npce-20251231.xsd#npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingSubawardsYear5"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_npce_ResearchAndDevelopmentArrangementWithFederalGovernmentApprovalForFundingSubawardsYear5_019b2ffc-6115-78b4-9f4c-4b291485762e" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementWithFederalGovernmentCustomerFundingToOffsetCostsIncurred_019b2ffc-6115-7a39-8495-fa602c49c1a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementWithFederalGovernmentCustomerFundingToOffsetCostsIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ResearchAndDevelopmentArrangementWithFederalGovernmentCustomerFundingToOffsetCostsIncurred_019b2ffc-6115-7a39-8495-fa602c49c1a6" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned_019b2ffc-6115-7666-8c10-e2a57126c87b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned_019b2ffc-6115-7666-8c10-e2a57126c87b" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019b2ffc-6115-7bb2-bfbd-db3830b287c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_019b2ffc-6115-7bb2-bfbd-db3830b287c9" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvertisingExpense_019b2ffc-ae68-7b3c-a823-cfa7acc10790" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdvertisingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_ff2935f0-ac2b-428b-90df-fb6bffc4ba4a" xlink:to="loc_us-gaap_AdvertisingExpense_019b2ffc-ae68-7b3c-a823-cfa7acc10790" xlink:type="arc" order="24"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/FairValueMeasurementsAssetsandLiabilitiesMeasuredatFairValueDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#FairValueMeasurementsAssetsandLiabilitiesMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/FairValueMeasurementsAssetsandLiabilitiesMeasuredatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a7766fef-5276-482b-b552-c3336fe0dc9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_82203418-2afe-433c-a360-35a5eff79386" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a7766fef-5276-482b-b552-c3336fe0dc9e" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_82203418-2afe-433c-a360-35a5eff79386" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4382d4c-d2ac-4769-ab1e-013402404a39" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_82203418-2afe-433c-a360-35a5eff79386" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4382d4c-d2ac-4769-ab1e-013402404a39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c4382d4c-d2ac-4769-ab1e-013402404a39_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4382d4c-d2ac-4769-ab1e-013402404a39" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c4382d4c-d2ac-4769-ab1e-013402404a39_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d66e8f83-fcb1-4858-a51d-4e6f8d8710cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c4382d4c-d2ac-4769-ab1e-013402404a39" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d66e8f83-fcb1-4858-a51d-4e6f8d8710cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_083f19c4-75de-493a-b5b8-996b62f977f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d66e8f83-fcb1-4858-a51d-4e6f8d8710cc" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_083f19c4-75de-493a-b5b8-996b62f977f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_bacf63e6-1f15-4d27-9198-ef3d298ce2e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d66e8f83-fcb1-4858-a51d-4e6f8d8710cc" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_bacf63e6-1f15-4d27-9198-ef3d298ce2e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_24563e85-dd36-485d-b6d3-e3a1230a77cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d66e8f83-fcb1-4858-a51d-4e6f8d8710cc" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_24563e85-dd36-485d-b6d3-e3a1230a77cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019cad03-2c5a-7b08-8637-94702f6d173d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a7766fef-5276-482b-b552-c3336fe0dc9e" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019cad03-2c5a-7b08-8637-94702f6d173d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_019cad03-2c5a-7c95-b746-455aa77d5761" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a7766fef-5276-482b-b552-c3336fe0dc9e" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_019cad03-2c5a-7c95-b746-455aa77d5761" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019cad03-2c5a-7381-bd46-f7858c620d00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a7766fef-5276-482b-b552-c3336fe0dc9e" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019cad03-2c5a-7381-bd46-f7858c620d00" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/BalanceSheetComponentsPropertyandEquipmentDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#BalanceSheetComponentsPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/BalanceSheetComponentsPropertyandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_665f5ba1-b243-4a5b-b99e-81c0e79c4ceb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_64606fb1-1304-4a85-9b5c-008e342df968" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_665f5ba1-b243-4a5b-b99e-81c0e79c4ceb" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_64606fb1-1304-4a85-9b5c-008e342df968" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d6be4f8e-6f4c-4ec8-ba0b-a9b190adb99c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_64606fb1-1304-4a85-9b5c-008e342df968" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d6be4f8e-6f4c-4ec8-ba0b-a9b190adb99c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d6be4f8e-6f4c-4ec8-ba0b-a9b190adb99c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d6be4f8e-6f4c-4ec8-ba0b-a9b190adb99c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_d6be4f8e-6f4c-4ec8-ba0b-a9b190adb99c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_813a10af-75a1-4032-a31c-4cc98c1f2276" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_d6be4f8e-6f4c-4ec8-ba0b-a9b190adb99c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_813a10af-75a1-4032-a31c-4cc98c1f2276" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_MachineryEquipmentFurnitureAndFixturesMember_a822c9b0-cedf-42c0-be30-dee27859a42f" xlink:href="npce-20251231.xsd#npce_MachineryEquipmentFurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_813a10af-75a1-4032-a31c-4cc98c1f2276" xlink:to="loc_npce_MachineryEquipmentFurnitureAndFixturesMember_a822c9b0-cedf-42c0-be30-dee27859a42f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ComputerEquipmentAndSoftwareMember_fd3950ea-c762-4be6-b876-566939b80f47" xlink:href="npce-20251231.xsd#npce_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_813a10af-75a1-4032-a31c-4cc98c1f2276" xlink:to="loc_npce_ComputerEquipmentAndSoftwareMember_fd3950ea-c762-4be6-b876-566939b80f47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_31036f9a-e2ee-4878-b92e-e14396e866f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_813a10af-75a1-4032-a31c-4cc98c1f2276" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_31036f9a-e2ee-4878-b92e-e14396e866f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_fd847057-fce5-435a-8f73-40584b21d862" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_665f5ba1-b243-4a5b-b99e-81c0e79c4ceb" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_fd847057-fce5-435a-8f73-40584b21d862" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_993ce882-e627-40b9-ad04-61a1ac17eb19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_665f5ba1-b243-4a5b-b99e-81c0e79c4ceb" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_993ce882-e627-40b9-ad04-61a1ac17eb19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_71a01e4c-5220-4129-9ef2-eae70acaeb71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_665f5ba1-b243-4a5b-b99e-81c0e79c4ceb" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_71a01e4c-5220-4129-9ef2-eae70acaeb71" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_f0d6f119-7b02-4388-bfff-b27f9558abd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_665f5ba1-b243-4a5b-b99e-81c0e79c4ceb" xlink:to="loc_us-gaap_Depreciation_f0d6f119-7b02-4388-bfff-b27f9558abd9" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/CommitmentsandContingenciesAdditionalInformationDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#CommitmentsandContingenciesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/CommitmentsandContingenciesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_4453b01e-5afc-43a6-8fa8-f18bb907579e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_LossContingenciesTable_4453b01e-5afc-43a6-8fa8-f18bb907579e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4800e6c7-89e6-4d74-be94-c4452cdeafd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_4453b01e-5afc-43a6-8fa8-f18bb907579e" xlink:to="loc_us-gaap_DebtInstrumentAxis_4800e6c7-89e6-4d74-be94-c4452cdeafd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4800e6c7-89e6-4d74-be94-c4452cdeafd5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4800e6c7-89e6-4d74-be94-c4452cdeafd5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4800e6c7-89e6-4d74-be94-c4452cdeafd5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_61539431-3aed-484e-a225-89061b653370" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4800e6c7-89e6-4d74-be94-c4452cdeafd5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_61539431-3aed-484e-a225-89061b653370" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_LeaseFacilityMember_e785c04d-21e7-4327-a302-899e7f8a8167" xlink:href="npce-20251231.xsd#npce_LeaseFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_61539431-3aed-484e-a225-89061b653370" xlink:to="loc_npce_LeaseFacilityMember_e785c04d-21e7-4327-a302-899e7f8a8167" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_f33ac7aa-ac68-4903-b5d3-b42d37661cdf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_4453b01e-5afc-43a6-8fa8-f18bb907579e" xlink:to="loc_srt_RangeAxis_f33ac7aa-ac68-4903-b5d3-b42d37661cdf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f33ac7aa-ac68-4903-b5d3-b42d37661cdf_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_f33ac7aa-ac68-4903-b5d3-b42d37661cdf" xlink:to="loc_srt_RangeMember_f33ac7aa-ac68-4903-b5d3-b42d37661cdf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3bcc9389-f796-4d09-a66e-174e3c0cfec1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_f33ac7aa-ac68-4903-b5d3-b42d37661cdf" xlink:to="loc_srt_RangeMember_3bcc9389-f796-4d09-a66e-174e3c0cfec1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_2b7f0f82-28c1-4056-a52b-787154c33ccf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3bcc9389-f796-4d09-a66e-174e3c0cfec1" xlink:to="loc_srt_MinimumMember_2b7f0f82-28c1-4056-a52b-787154c33ccf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0947f253-de41-4b04-a7bc-724fc1c293fc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3bcc9389-f796-4d09-a66e-174e3c0cfec1" xlink:to="loc_srt_MaximumMember_0947f253-de41-4b04-a7bc-724fc1c293fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_3533edcf-dab2-4f02-b298-c84b0aa36b62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_4453b01e-5afc-43a6-8fa8-f18bb907579e" xlink:to="loc_us-gaap_LitigationStatusAxis_3533edcf-dab2-4f02-b298-c84b0aa36b62" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_3533edcf-dab2-4f02-b298-c84b0aa36b62_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_3533edcf-dab2-4f02-b298-c84b0aa36b62" xlink:to="loc_us-gaap_LitigationStatusDomain_3533edcf-dab2-4f02-b298-c84b0aa36b62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_7e604a97-351a-46d3-b57f-6808b7b1a24d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_3533edcf-dab2-4f02-b298-c84b0aa36b62" xlink:to="loc_us-gaap_LitigationStatusDomain_7e604a97-351a-46d3-b57f-6808b7b1a24d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_57fef730-7d24-4220-8523-b6b84b24b0b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_7e604a97-351a-46d3-b57f-6808b7b1a24d" xlink:to="loc_us-gaap_PendingLitigationMember_57fef730-7d24-4220-8523-b6b84b24b0b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019c4638-d97f-78c3-8f54-71bdc63517cb" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_4453b01e-5afc-43a6-8fa8-f18bb907579e" xlink:to="loc_srt_CounterpartyNameAxis_019c4638-d97f-78c3-8f54-71bdc63517cb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c4638-d97f-78c3-8f54-71bdc63517cb_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019c4638-d97f-78c3-8f54-71bdc63517cb" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c4638-d97f-78c3-8f54-71bdc63517cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c4638-d97f-7372-81c0-01fbba896c72" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019c4638-d97f-78c3-8f54-71bdc63517cb" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c4638-d97f-7372-81c0-01fbba896c72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DIXIMedicalUSACorpMember_019c4639-bae0-7dd8-900c-b332e76a360e" xlink:href="npce-20251231.xsd#npce_DIXIMedicalUSACorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c4638-d97f-7372-81c0-01fbba896c72" xlink:to="loc_npce_DIXIMedicalUSACorpMember_019c4639-bae0-7dd8-900c-b332e76a360e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OperatingLeaseRenewalTerm_c3115fb8-5266-4d1a-a654-32a46e8d5a67" xlink:href="npce-20251231.xsd#npce_OperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_OperatingLeaseRenewalTerm_c3115fb8-5266-4d1a-a654-32a46e8d5a67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_a8d14824-86ec-41ea-8fa6-01256a13ce70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_a8d14824-86ec-41ea-8fa6-01256a13ce70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OperatingLeasesAnnualRentalPayments_8a7d3eef-735c-4dac-97ed-8823627de3a3" xlink:href="npce-20251231.xsd#npce_OperatingLeasesAnnualRentalPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_OperatingLeasesAnnualRentalPayments_8a7d3eef-735c-4dac-97ed-8823627de3a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_fca15d33-c345-4772-9b4b-07f794ad4f5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_OperatingLeaseCost_fca15d33-c345-4772-9b4b-07f794ad4f5c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_3f3e6be0-c816-4524-bfd2-70a5421cde42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_3f3e6be0-c816-4524-bfd2-70a5421cde42" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_516b922f-6b11-45e3-bed3-02938cca1134" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_516b922f-6b11-45e3-bed3-02938cca1134" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasePayments_e47516d4-904d-43cf-b463-e6467cf6633f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeasePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_OperatingLeasePayments_e47516d4-904d-43cf-b463-e6467cf6633f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DistributionAgreementInitialTerm_eb4e4467-0cec-4b52-9a4b-bb5e986f57f5" xlink:href="npce-20251231.xsd#npce_DistributionAgreementInitialTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_DistributionAgreementInitialTerm_eb4e4467-0cec-4b52-9a4b-bb5e986f57f5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_f0af1482-765d-4e55-b9ed-0124c0426f5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PurchaseObligationDueInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_PurchaseObligationDueInNextTwelveMonths_f0af1482-765d-4e55-b9ed-0124c0426f5d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_PurchaseObligationMinimumIncreasePercentageInNextTwoYears_01ef7653-1337-4c82-9219-fc63a63cde17" xlink:href="npce-20251231.xsd#npce_PurchaseObligationMinimumIncreasePercentageInNextTwoYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_PurchaseObligationMinimumIncreasePercentageInNextTwoYears_01ef7653-1337-4c82-9219-fc63a63cde17" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DistributionAgreementRenewalTerm_76109b73-1778-47ab-be20-5baafff33fc5" xlink:href="npce-20251231.xsd#npce_DistributionAgreementRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_DistributionAgreementRenewalTerm_76109b73-1778-47ab-be20-5baafff33fc5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DistributionAgreementPeriodForNoticeOfNonRenewal_cb38e9fd-51a8-46a7-a94e-afa5bf07e7c1" xlink:href="npce-20251231.xsd#npce_DistributionAgreementPeriodForNoticeOfNonRenewal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_DistributionAgreementPeriodForNoticeOfNonRenewal_cb38e9fd-51a8-46a7-a94e-afa5bf07e7c1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DistributionAgreementInventory_019c4637-17ba-7e21-aa8a-2f2655480bb2" xlink:href="npce-20251231.xsd#npce_DistributionAgreementInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_DistributionAgreementInventory_019c4637-17ba-7e21-aa8a-2f2655480bb2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_IndemnificationLiabilityOfficersAndDirectors_bc4c6da5-8722-40e7-86e4-2cbf8d9b7e90" xlink:href="npce-20251231.xsd#npce_IndemnificationLiabilityOfficersAndDirectors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_npce_IndemnificationLiabilityOfficersAndDirectors_bc4c6da5-8722-40e7-86e4-2cbf8d9b7e90" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_6c589c75-fb7f-4d7d-a3cf-9c55e952f686" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c8007e68-2464-4181-99a7-c6197bba0ce8" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_6c589c75-fb7f-4d7d-a3cf-9c55e952f686" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/DebtAdditionalInformationDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#DebtAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/DebtAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019b3042-f04e-7995-b743-927d385ad083" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_us-gaap_DebtInstrumentAxis_019b3042-f04e-7995-b743-927d385ad083" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019b3042-f04e-7995-b743-927d385ad083_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019b3042-f04e-7995-b743-927d385ad083" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019b3042-f04e-7995-b743-927d385ad083_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019b3042-f04e-7d55-a514-8e0fe774b6e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019b3042-f04e-7995-b743-927d385ad083" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019b3042-f04e-7d55-a514-8e0fe774b6e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_CRGTermLoanAgreementMember_019b3042-f04e-7511-9625-78ca24b55dcd" xlink:href="npce-20251231.xsd#npce_CRGTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019b3042-f04e-7d55-a514-8e0fe774b6e2" xlink:to="loc_npce_CRGTermLoanAgreementMember_019b3042-f04e-7511-9625-78ca24b55dcd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_MidCapAgreementMember_019b3043-3a9a-7920-9e13-612171964e55" xlink:href="npce-20251231.xsd#npce_MidCapAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019b3042-f04e-7d55-a514-8e0fe774b6e2" xlink:to="loc_npce_MidCapAgreementMember_019b3043-3a9a-7920-9e13-612171964e55" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019b3042-f04e-7742-a632-9f09a72be052" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_srt_RangeAxis_019b3042-f04e-7742-a632-9f09a72be052" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019b3042-f04e-7742-a632-9f09a72be052_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019b3042-f04e-7742-a632-9f09a72be052" xlink:to="loc_srt_RangeMember_019b3042-f04e-7742-a632-9f09a72be052_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019b3042-f04e-7efe-8daa-ba1ebd8dc47e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019b3042-f04e-7742-a632-9f09a72be052" xlink:to="loc_srt_RangeMember_019b3042-f04e-7efe-8daa-ba1ebd8dc47e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019b3042-f04e-79c8-b648-2d5e342035ff" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019b3042-f04e-7efe-8daa-ba1ebd8dc47e" xlink:to="loc_srt_MinimumMember_019b3042-f04e-79c8-b648-2d5e342035ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019b3042-f04e-7097-a499-7b5041fed67f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019b3042-f04e-7efe-8daa-ba1ebd8dc47e" xlink:to="loc_srt_MaximumMember_019b3042-f04e-7097-a499-7b5041fed67f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019b3042-f04e-7d41-89de-9ae022dbbd39" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019b3042-f04e-7d41-89de-9ae022dbbd39" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-7d41-89de-9ae022dbbd39_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019b3042-f04e-7d41-89de-9ae022dbbd39" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-7d41-89de-9ae022dbbd39_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-76cd-9473-5f3d641ffb02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019b3042-f04e-7d41-89de-9ae022dbbd39" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-76cd-9473-5f3d641ffb02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_PaymentInCashMember_019b3042-f04e-7788-b371-2878810e90c0" xlink:href="npce-20251231.xsd#npce_PaymentInCashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-76cd-9473-5f3d641ffb02" xlink:to="loc_npce_PaymentInCashMember_019b3042-f04e-7788-b371-2878810e90c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentInKindPIKNoteMember_019b3042-f04e-7ef3-980e-6a61c5db74d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentInKindPIKNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-76cd-9473-5f3d641ffb02" xlink:to="loc_us-gaap_PaymentInKindPIKNoteMember_019b3042-f04e-7ef3-980e-6a61c5db74d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_MidTermNoteMember_019b3043-3a9a-7c1b-a2a0-2526c52a0350" xlink:href="npce-20251231.xsd#npce_MidTermNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019b3042-f04e-76cd-9473-5f3d641ffb02" xlink:to="loc_npce_MidTermNoteMember_019b3043-3a9a-7c1b-a2a0-2526c52a0350" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_019b3043-3a9a-7b10-a8d3-2144e1dd965f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_019b3043-3a9a-7b10-a8d3-2144e1dd965f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019b3043-3a9a-7b10-a8d3-2144e1dd965f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019b3043-3a9a-7b10-a8d3-2144e1dd965f" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019b3043-3a9a-7b10-a8d3-2144e1dd965f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019b3043-3a9a-7ae3-b691-1fee5809493d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019b3043-3a9a-7b10-a8d3-2144e1dd965f" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019b3043-3a9a-7ae3-b691-1fee5809493d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_SeriesBRedeemableConvertiblePreferredStockMember_019b3043-3a9a-7580-a5cc-be770baac77b" xlink:href="npce-20251231.xsd#npce_SeriesBRedeemableConvertiblePreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019b3043-3a9a-7ae3-b691-1fee5809493d" xlink:to="loc_npce_SeriesBRedeemableConvertiblePreferredStockMember_019b3043-3a9a-7580-a5cc-be770baac77b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c463d-cc77-7d37-a808-38226efda82f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019b3043-3a9a-7ae3-b691-1fee5809493d" xlink:to="loc_us-gaap_CommonStockMember_019c463d-cc77-7d37-a808-38226efda82f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019b3043-3a9a-77d9-b7ea-17f4be9c6978" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_us-gaap_CreditFacilityAxis_019b3043-3a9a-77d9-b7ea-17f4be9c6978" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019b3043-3a9a-77d9-b7ea-17f4be9c6978_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019b3043-3a9a-77d9-b7ea-17f4be9c6978" xlink:to="loc_us-gaap_CreditFacilityDomain_019b3043-3a9a-77d9-b7ea-17f4be9c6978_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019b3043-3a9a-73d0-b9c0-e37162b939f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019b3043-3a9a-77d9-b7ea-17f4be9c6978" xlink:to="loc_us-gaap_CreditFacilityDomain_019b3043-3a9a-73d0-b9c0-e37162b939f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019b3043-3a9a-7df4-82ed-544a5086d394" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019b3043-3a9a-73d0-b9c0-e37162b939f2" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019b3043-3a9a-7df4-82ed-544a5086d394" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019b3043-3a9a-764e-afdf-21ad14712537" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_us-gaap_VariableRateAxis_019b3043-3a9a-764e-afdf-21ad14712537" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019b3043-3a9a-764e-afdf-21ad14712537_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019b3043-3a9a-764e-afdf-21ad14712537" xlink:to="loc_us-gaap_VariableRateDomain_019b3043-3a9a-764e-afdf-21ad14712537_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019b3043-3a9a-7a70-abd1-28bd814c2015" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019b3043-3a9a-764e-afdf-21ad14712537" xlink:to="loc_us-gaap_VariableRateDomain_019b3043-3a9a-7a70-abd1-28bd814c2015" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019b3043-3a9a-7753-b39d-e5ac5c67ab7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019b3043-3a9a-7a70-abd1-28bd814c2015" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019b3043-3a9a-7753-b39d-e5ac5c67ab7e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_SecuredOvernightFinancingRateFloorMember_019b3043-3a9a-7a48-8fd5-aed7acff81e9" xlink:href="npce-20251231.xsd#npce_SecuredOvernightFinancingRateFloorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019b3043-3a9a-7a70-abd1-28bd814c2015" xlink:to="loc_npce_SecuredOvernightFinancingRateFloorMember_019b3043-3a9a-7a48-8fd5-aed7acff81e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019b3043-3a9a-70b2-b077-ca7a013f7ade" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c3b78b63-8538-406e-97b5-9b20b18a9fa6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019b3043-3a9a-70b2-b077-ca7a013f7ade" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-70b2-b077-ca7a013f7ade_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019b3043-3a9a-70b2-b077-ca7a013f7ade" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-70b2-b077-ca7a013f7ade_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-76f5-9ffe-0489a55bc1c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_019b3043-3a9a-70b2-b077-ca7a013f7ade" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-76f5-9ffe-0489a55bc1c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019b3043-3a9a-79c5-b852-f818ee990de2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-76f5-9ffe-0489a55bc1c9" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_019b3043-3a9a-79c5-b852-f818ee990de2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019b3043-3a9a-79cf-98c0-c0190f1525ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-76f5-9ffe-0489a55bc1c9" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_019b3043-3a9a-79cf-98c0-c0190f1525ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_019b3043-3a9a-73c9-af49-1619edaa8a24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRedemptionPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-76f5-9ffe-0489a55bc1c9" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_019b3043-3a9a-73c9-af49-1619edaa8a24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentRedemptionPeriodThereafterMember_019b3043-3a9a-7eb8-90d8-39b00d6fd398" xlink:href="npce-20251231.xsd#npce_DebtInstrumentRedemptionPeriodThereafterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_019b3043-3a9a-76f5-9ffe-0489a55bc1c9" xlink:to="loc_npce_DebtInstrumentRedemptionPeriodThereafterMember_019b3043-3a9a-7eb8-90d8-39b00d6fd398" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019b3042-f04e-73c0-8e87-36db28de9cef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019b3042-f04e-73c0-8e87-36db28de9cef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019b3042-f04e-74f9-a9d9-00e7bd6ffc7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019b3042-f04e-74f9-a9d9-00e7bd6ffc7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019b3042-f04e-72d8-a578-11e7025b3b8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019b3042-f04e-72d8-a578-11e7025b3b8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019b3042-f04e-7439-935e-670a2bc92149" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019b3042-f04e-7439-935e-670a2bc92149" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentPaidInKindIncreaseToPrincipal_019b3042-f04e-7a3c-896c-e0190a859cfd" xlink:href="npce-20251231.xsd#npce_DebtInstrumentPaidInKindIncreaseToPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_DebtInstrumentPaidInKindIncreaseToPrincipal_019b3042-f04e-7a3c-896c-e0190a859cfd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentTermExtension_019b3042-f04e-7d62-b797-52e050adb8d3" xlink:href="npce-20251231.xsd#npce_DebtInstrumentTermExtension"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_DebtInstrumentTermExtension_019b3042-f04e-7d62-b797-52e050adb8d3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentRedemptionFeePercent_019b3043-3a9a-7a9a-bc8a-7f0c828e2762" xlink:href="npce-20251231.xsd#npce_DebtInstrumentRedemptionFeePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_DebtInstrumentRedemptionFeePercent_019b3043-3a9a-7a9a-bc8a-7f0c828e2762" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentCovenantMinimumAnnualNetRevenue_019b3043-3a9a-79da-a97d-aaaaae7a331e" xlink:href="npce-20251231.xsd#npce_DebtInstrumentCovenantMinimumAnnualNetRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_DebtInstrumentCovenantMinimumAnnualNetRevenue_019b3043-3a9a-79da-a97d-aaaaae7a331e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFeeAmount_019b3043-3a9a-78b8-9d57-168454363459" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentFeeAmount_019b3043-3a9a-78b8-9d57-168454363459" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_019b3043-3a9a-7634-9fe0-c22caefd956d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_019b3043-3a9a-7634-9fe0-c22caefd956d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_019c8bd8-9e0b-7ce8-82fa-bdf9617d1cd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_019c8bd8-9e0b-7ce8-82fa-bdf9617d1cd5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_WarrantLiabilityNoncurrent_019b3043-3a9a-7dd3-a9ac-9c7af0fe8575" xlink:href="npce-20251231.xsd#npce_WarrantLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_WarrantLiabilityNoncurrent_019b3043-3a9a-7dd3-a9ac-9c7af0fe8575" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_019b3043-3a9a-7be3-bef9-ba60f484f4d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_019b3043-3a9a-7be3-bef9-ba60f484f4d8" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepaidPrincipal_019b3043-3a9a-7cb2-ad36-b4a4abbaf6e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentRepaidPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentRepaidPrincipal_019b3043-3a9a-7cb2-ad36-b4a4abbaf6e0" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019b3043-3a9a-7ffc-a954-f50661c26941" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_InterestExpenseDebt_019b3043-3a9a-7ffc-a954-f50661c26941" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019b3043-3a9a-7046-b5a6-54f608a40e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_019b3043-3a9a-7046-b5a6-54f608a40e5b" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019b3043-3a9a-738e-b77c-c4f878d14a2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019b3043-3a9a-738e-b77c-c4f878d14a2f" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_019b3043-3a9a-70db-a0b8-769fc58705c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_019b3043-3a9a-70db-a0b8-769fc58705c0" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019b3043-3a9a-7882-a45d-ec87046ccb25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019b3043-3a9a-7882-a45d-ec87046ccb25" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentPrincipalPaymentNumberOfInstallments_019b3043-3a9a-7b40-ad58-ab03242648d5" xlink:href="npce-20251231.xsd#npce_DebtInstrumentPrincipalPaymentNumberOfInstallments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_DebtInstrumentPrincipalPaymentNumberOfInstallments_019b3043-3a9a-7b40-ad58-ab03242648d5" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019b3043-3a9a-7ae8-93b3-08be902e5ee3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019b3043-3a9a-7ae8-93b3-08be902e5ee3" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_019b3043-3a9a-7d5c-80bc-c2a2ea171243" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_019b3043-3a9a-7d5c-80bc-c2a2ea171243" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentPrepaymentFeePercent_019b3043-3a9a-7c17-84f2-9248dc04ccd0" xlink:href="npce-20251231.xsd#npce_DebtInstrumentPrepaymentFeePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_DebtInstrumentPrepaymentFeePercent_019b3043-3a9a-7c17-84f2-9248dc04ccd0" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_AnnualAdministrativeFeePayable_019b3043-6bb9-76ef-aea3-7b38e6396699" xlink:href="npce-20251231.xsd#npce_AnnualAdministrativeFeePayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b8d34bab-c162-461f-8f80-db9cdec0e53b" xlink:to="loc_npce_AnnualAdministrativeFeePayable_019b3043-6bb9-76ef-aea3-7b38e6396699" xlink:type="arc" order="23"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/DebtMaturitiesofDebtDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#DebtMaturitiesofDebtDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/DebtMaturitiesofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_f7cd27f1-2b35-4045-8dda-8ffc76af6b11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_DebtInstrumentTable_f7cd27f1-2b35-4045-8dda-8ffc76af6b11" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9c1ddf26-59fe-4e9d-9884-7906826603a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f7cd27f1-2b35-4045-8dda-8ffc76af6b11" xlink:to="loc_us-gaap_DebtInstrumentAxis_9c1ddf26-59fe-4e9d-9884-7906826603a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9c1ddf26-59fe-4e9d-9884-7906826603a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9c1ddf26-59fe-4e9d-9884-7906826603a4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9c1ddf26-59fe-4e9d-9884-7906826603a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_da8a4da7-09c6-4384-b07f-4b05d284e4eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9c1ddf26-59fe-4e9d-9884-7906826603a4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_da8a4da7-09c6-4384-b07f-4b05d284e4eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_MidCapAgreementMember_019b301f-d74c-7781-acef-d30da338f8b3" xlink:href="npce-20251231.xsd#npce_MidCapAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_da8a4da7-09c6-4384-b07f-4b05d284e4eb" xlink:to="loc_npce_MidCapAgreementMember_019b301f-d74c-7781-acef-d30da338f8b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019b301f-d74c-72d6-a0f0-b9143fce7312" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f7cd27f1-2b35-4045-8dda-8ffc76af6b11" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019b301f-d74c-72d6-a0f0-b9143fce7312" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019b301f-d74c-72d6-a0f0-b9143fce7312_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019b301f-d74c-72d6-a0f0-b9143fce7312" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019b301f-d74c-72d6-a0f0-b9143fce7312_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019b301f-d74c-7bda-9ab7-189b572e0db1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019b301f-d74c-72d6-a0f0-b9143fce7312" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019b301f-d74c-7bda-9ab7-189b572e0db1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_MidTermNoteMember_019b301f-d74c-77e9-8a0f-c3e4b065fa72" xlink:href="npce-20251231.xsd#npce_MidTermNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019b301f-d74c-7bda-9ab7-189b572e0db1" xlink:to="loc_npce_MidTermNoteMember_019b301f-d74c-77e9-8a0f-c3e4b065fa72" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NatureOfExpenseAxis_019c70fc-922c-73e1-a930-b53a4847bf19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NatureOfExpenseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f7cd27f1-2b35-4045-8dda-8ffc76af6b11" xlink:to="loc_us-gaap_NatureOfExpenseAxis_019c70fc-922c-73e1-a930-b53a4847bf19" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019c70fc-922c-73e1-a930-b53a4847bf19_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterimPeriodCostsNotAllocableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NatureOfExpenseAxis_019c70fc-922c-73e1-a930-b53a4847bf19" xlink:to="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019c70fc-922c-73e1-a930-b53a4847bf19_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019c70fc-922c-7b42-9939-76c0b2d3a008" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterimPeriodCostsNotAllocableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NatureOfExpenseAxis_019c70fc-922c-73e1-a930-b53a4847bf19" xlink:to="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019c70fc-922c-7b42-9939-76c0b2d3a008" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_EstimatedInterestAndAdministrativeFeeMember_019c70fc-ee16-7284-964d-b124b58dd621" xlink:href="npce-20251231.xsd#npce_EstimatedInterestAndAdministrativeFeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019c70fc-922c-7b42-9939-76c0b2d3a008" xlink:to="loc_npce_EstimatedInterestAndAdministrativeFeeMember_019c70fc-ee16-7284-964d-b124b58dd621" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_PrincipalAndExitFeeMember_019c70fd-54f8-70ed-86fd-e5f488902e74" xlink:href="npce-20251231.xsd#npce_PrincipalAndExitFeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019c70fc-922c-7b42-9939-76c0b2d3a008" xlink:to="loc_npce_PrincipalAndExitFeeMember_019c70fd-54f8-70ed-86fd-e5f488902e74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_eade523e-2da8-441b-81ab-b2bf97c5764c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_eade523e-2da8-441b-81ab-b2bf97c5764c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_f861d738-dbd5-4e6f-85f6-62b2bcd5c5b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_f861d738-dbd5-4e6f-85f6-62b2bcd5c5b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019b301f-d74c-779a-a252-bce3d38ce5f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_019b301f-d74c-779a-a252-bce3d38ce5f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019b301f-d74c-70b4-8ff9-664967edcc52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_019b301f-d74c-70b4-8ff9-664967edcc52" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_019b6f24-98a0-799a-ba96-41b2ce9f432e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_019b6f24-98a0-799a-ba96-41b2ce9f432e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_1f85e86d-cadd-4a8d-a5e4-4408ec06b0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_1f85e86d-cadd-4a8d-a5e4-4408ec06b0dc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_3894f468-e586-4078-b3be-934c8f344751" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_3894f468-e586-4078-b3be-934c8f344751" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_DebtInstrumentUnamortizedInterestCost_c320106e-df60-44dd-974e-2b5d2a65b3f2" xlink:href="npce-20251231.xsd#npce_DebtInstrumentUnamortizedInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_npce_DebtInstrumentUnamortizedInterestCost_c320106e-df60-44dd-974e-2b5d2a65b3f2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_86b22f6c-01e2-4693-aaba-95b180de60fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_899e23fe-d331-4bcd-a7bb-ecf133f180a0" xlink:to="loc_us-gaap_LongTermDebt_86b22f6c-01e2-4693-aaba-95b180de60fa" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/CommonStockStockbyClassDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#CommonStockStockbyClassDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/CommonStockStockbyClassDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_650374a2-4fef-4369-80b6-28972b50826d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_9afd233a-c807-4fa7-ab4e-2661fa0d432b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_650374a2-4fef-4369-80b6-28972b50826d" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_9afd233a-c807-4fa7-ab4e-2661fa0d432b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_870b6320-80e7-439d-a899-1bfd9d235743" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_9afd233a-c807-4fa7-ab4e-2661fa0d432b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_870b6320-80e7-439d-a899-1bfd9d235743" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_870b6320-80e7-439d-a899-1bfd9d235743_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_870b6320-80e7-439d-a899-1bfd9d235743" xlink:to="loc_us-gaap_ClassOfStockDomain_870b6320-80e7-439d-a899-1bfd9d235743_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_870b6320-80e7-439d-a899-1bfd9d235743" xlink:to="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OutstandingOptions2021PlanMember_d94d380a-0227-410f-a916-6436aa0e868e" xlink:href="npce-20251231.xsd#npce_OutstandingOptions2021PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:to="loc_npce_OutstandingOptions2021PlanMember_d94d380a-0227-410f-a916-6436aa0e868e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OptionsAvailableForGrant2021PlanMember_af2b1350-509a-491a-a134-66fb2ac6e311" xlink:href="npce-20251231.xsd#npce_OptionsAvailableForGrant2021PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:to="loc_npce_OptionsAvailableForGrant2021PlanMember_af2b1350-509a-491a-a134-66fb2ac6e311" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OutstandingOptions2023InducementPlanMember_679e7128-2012-436d-8030-b6ce08b15d39" xlink:href="npce-20251231.xsd#npce_OutstandingOptions2023InducementPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:to="loc_npce_OutstandingOptions2023InducementPlanMember_679e7128-2012-436d-8030-b6ce08b15d39" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OptionsRestrictedStockUnit2021PlanMember_d1143eb7-6244-42fb-b7e3-e1b2b1e57188" xlink:href="npce-20251231.xsd#npce_OptionsRestrictedStockUnit2021PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:to="loc_npce_OptionsRestrictedStockUnit2021PlanMember_d1143eb7-6244-42fb-b7e3-e1b2b1e57188" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_CommonStockAvailableForESPPMember_0fa6b47b-5149-46ec-a78d-9c1861b96a6b" xlink:href="npce-20251231.xsd#npce_CommonStockAvailableForESPPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f6d637c1-79d7-4bf1-a841-ddc5dd3e459f" xlink:to="loc_npce_CommonStockAvailableForESPPMember_0fa6b47b-5149-46ec-a78d-9c1861b96a6b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_e375fdb8-5abb-4434-92cb-dacc6f86a964" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_650374a2-4fef-4369-80b6-28972b50826d" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_e375fdb8-5abb-4434-92cb-dacc6f86a964" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StockPlansAdditionalInformationDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#StockPlansAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StockPlansAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_8682677f-2d5a-4efa-b825-07fc3da05e41" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_us-gaap_PlanNameAxis_8682677f-2d5a-4efa-b825-07fc3da05e41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_8682677f-2d5a-4efa-b825-07fc3da05e41_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_8682677f-2d5a-4efa-b825-07fc3da05e41" xlink:to="loc_us-gaap_PlanNameDomain_8682677f-2d5a-4efa-b825-07fc3da05e41_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_87fa3d2e-1d35-482f-8c93-cba7ad3d3d0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_8682677f-2d5a-4efa-b825-07fc3da05e41" xlink:to="loc_us-gaap_PlanNameDomain_87fa3d2e-1d35-482f-8c93-cba7ad3d3d0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_A2021StockEquityIncentivePlanMember_54a580cc-bd4b-48c1-88f5-5d4a03968e6e" xlink:href="npce-20251231.xsd#npce_A2021StockEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_87fa3d2e-1d35-482f-8c93-cba7ad3d3d0c" xlink:to="loc_npce_A2021StockEquityIncentivePlanMember_54a580cc-bd4b-48c1-88f5-5d4a03968e6e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_InducementPlanMember_21c5c84a-b385-4304-9b25-d0eed8885675" xlink:href="npce-20251231.xsd#npce_InducementPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_87fa3d2e-1d35-482f-8c93-cba7ad3d3d0c" xlink:to="loc_npce_InducementPlanMember_21c5c84a-b385-4304-9b25-d0eed8885675" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_A2021EmployeeStockPurchasePlanMember_e04fb987-18df-4c46-9a35-d1865cac9f04" xlink:href="npce-20251231.xsd#npce_A2021EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_87fa3d2e-1d35-482f-8c93-cba7ad3d3d0c" xlink:to="loc_npce_A2021EmployeeStockPurchasePlanMember_e04fb987-18df-4c46-9a35-d1865cac9f04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_a6edaf0e-0534-4519-b3a1-c89fbd5baccb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_us-gaap_AwardTypeAxis_a6edaf0e-0534-4519-b3a1-c89fbd5baccb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6edaf0e-0534-4519-b3a1-c89fbd5baccb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_a6edaf0e-0534-4519-b3a1-c89fbd5baccb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6edaf0e-0534-4519-b3a1-c89fbd5baccb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_547b0c34-0169-49eb-89f5-bf7d1330e4b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_a6edaf0e-0534-4519-b3a1-c89fbd5baccb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_547b0c34-0169-49eb-89f5-bf7d1330e4b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_87cc468b-4b31-470c-8e30-7ab2875f2e60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_547b0c34-0169-49eb-89f5-bf7d1330e4b7" xlink:to="loc_us-gaap_EmployeeStockOptionMember_87cc468b-4b31-470c-8e30-7ab2875f2e60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_0731f20f-10d2-45b8-afbf-3335380197c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_0731f20f-10d2-45b8-afbf-3335380197c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_0731f20f-10d2-45b8-afbf-3335380197c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_0731f20f-10d2-45b8-afbf-3335380197c5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_0731f20f-10d2-45b8-afbf-3335380197c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_0454ce6a-49e8-4931-ae28-54c3085b3cf5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_0731f20f-10d2-45b8-afbf-3335380197c5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_0454ce6a-49e8-4931-ae28-54c3085b3cf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_e0b6f091-d416-42d1-9420-93da743fc586" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_0454ce6a-49e8-4931-ae28-54c3085b3cf5" xlink:to="loc_us-gaap_SubsequentEventMember_e0b6f091-d416-42d1-9420-93da743fc586" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_ddce024c-d2d0-4457-aafb-54346e4a905a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_srt_StatementScenarioAxis_ddce024c-d2d0-4457-aafb-54346e4a905a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_ddce024c-d2d0-4457-aafb-54346e4a905a_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_ddce024c-d2d0-4457-aafb-54346e4a905a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_ddce024c-d2d0-4457-aafb-54346e4a905a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_bb48eb0e-b704-4f63-a2cc-0f0f7af62db4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_ddce024c-d2d0-4457-aafb-54346e4a905a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_bb48eb0e-b704-4f63-a2cc-0f0f7af62db4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_5d36c404-c433-42e4-b1eb-14c1c19d5e30" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_bb48eb0e-b704-4f63-a2cc-0f0f7af62db4" xlink:to="loc_srt_ScenarioForecastMember_5d36c404-c433-42e4-b1eb-14c1c19d5e30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_5a7a902a-558a-480e-bca0-1cbe6d63a91a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_srt_RangeAxis_5a7a902a-558a-480e-bca0-1cbe6d63a91a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5a7a902a-558a-480e-bca0-1cbe6d63a91a_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_5a7a902a-558a-480e-bca0-1cbe6d63a91a" xlink:to="loc_srt_RangeMember_5a7a902a-558a-480e-bca0-1cbe6d63a91a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_71653d34-4b3b-44b3-89d0-099f3b81704d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_5a7a902a-558a-480e-bca0-1cbe6d63a91a" xlink:to="loc_srt_RangeMember_71653d34-4b3b-44b3-89d0-099f3b81704d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_1ecef57f-e25b-4fb2-9e4b-714d34caaf42" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_71653d34-4b3b-44b3-89d0-099f3b81704d" xlink:to="loc_srt_MinimumMember_1ecef57f-e25b-4fb2-9e4b-714d34caaf42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_d995efc7-b4d1-4279-ab40-565a0aac4289" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_71653d34-4b3b-44b3-89d0-099f3b81704d" xlink:to="loc_srt_MaximumMember_d995efc7-b4d1-4279-ab40-565a0aac4289" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_06fd66f6-950a-41fe-94f3-4599b02cede7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_srt_TitleOfIndividualAxis_06fd66f6-950a-41fe-94f3-4599b02cede7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_06fd66f6-950a-41fe-94f3-4599b02cede7_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_06fd66f6-950a-41fe-94f3-4599b02cede7" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_06fd66f6-950a-41fe-94f3-4599b02cede7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_64915acc-4ddc-4c91-be1e-3bf0d242f9ad" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_06fd66f6-950a-41fe-94f3-4599b02cede7" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_64915acc-4ddc-4c91-be1e-3bf0d242f9ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefExecutiveOfficerMember_14113ae7-53f7-4b41-a455-ad2634e5a5e9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ChiefExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_64915acc-4ddc-4c91-be1e-3bf0d242f9ad" xlink:to="loc_srt_ChiefExecutiveOfficerMember_14113ae7-53f7-4b41-a455-ad2634e5a5e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_6ee2ae18-f59c-4ba9-b138-959cfd70182b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8617e8f9-a1ed-4068-ba3f-b2bb2755920a" xlink:to="loc_us-gaap_GranteeStatusAxis_6ee2ae18-f59c-4ba9-b138-959cfd70182b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_6ee2ae18-f59c-4ba9-b138-959cfd70182b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_6ee2ae18-f59c-4ba9-b138-959cfd70182b" xlink:to="loc_us-gaap_GranteeStatusDomain_6ee2ae18-f59c-4ba9-b138-959cfd70182b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_ded898b8-05bc-40f2-9beb-97966b47dd5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_6ee2ae18-f59c-4ba9-b138-959cfd70182b" xlink:to="loc_us-gaap_GranteeStatusDomain_ded898b8-05bc-40f2-9beb-97966b47dd5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_6523bb67-958b-4e6b-be37-500dea6c130d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedPaymentArrangementEmployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_ded898b8-05bc-40f2-9beb-97966b47dd5d" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_6523bb67-958b-4e6b-be37-500dea6c130d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_12266429-c72c-44d6-bc6e-dd026da7ce92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_12266429-c72c-44d6-bc6e-dd026da7ce92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockGrantedTo10StockholderMinimumPercent_034bf430-b92f-4c9f-beb7-366ff8fab706" xlink:href="npce-20251231.xsd#npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockGrantedTo10StockholderMinimumPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockGrantedTo10StockholderMinimumPercent_034bf430-b92f-4c9f-beb7-366ff8fab706" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_7ca5652c-8d7a-4c10-8517-a8f7e550bf19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_7ca5652c-8d7a-4c10-8517-a8f7e550bf19" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_c3eecd9c-c6a3-4121-9b58-9e9545e74d69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_c3eecd9c-c6a3-4121-9b58-9e9545e74d69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_91fbbb4d-0931-4e55-925b-be5bc6cb39b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_91fbbb4d-0931-4e55-925b-be5bc6cb39b5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_6ee41f13-677f-45fa-aa82-554be0925ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_6ee41f13-677f-45fa-aa82-554be0925ff3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_69a08399-d4fc-4ac5-920c-9edcf47467aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_69a08399-d4fc-4ac5-920c-9edcf47467aa" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_ff57472a-69c0-46cb-bd54-65737c02e987" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_ff57472a-69c0-46cb-bd54-65737c02e987" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_EmployeeStockPurchasePlanLengthOfOfferingPeriod_022ef298-bdf0-4ac0-a51d-e73c9945ad4c" xlink:href="npce-20251231.xsd#npce_EmployeeStockPurchasePlanLengthOfOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_npce_EmployeeStockPurchasePlanLengthOfOfferingPeriod_022ef298-bdf0-4ac0-a51d-e73c9945ad4c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_51768e6b-3a6e-438a-a200-49b183ae1506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_51768e6b-3a6e-438a-a200-49b183ae1506" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_7211141d-3ca1-4b21-a448-9cbf1b65e96f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_7211141d-3ca1-4b21-a448-9cbf1b65e96f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_EmployeeStockPurchasePlanOfferingPeriod_7f62d417-97fa-4248-9ee5-2eaa471b2c6a" xlink:href="npce-20251231.xsd#npce_EmployeeStockPurchasePlanOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_npce_EmployeeStockPurchasePlanOfferingPeriod_7f62d417-97fa-4248-9ee5-2eaa471b2c6a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_817b4e0a-42a9-4452-8f68-2736c617415d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_817b4e0a-42a9-4452-8f68-2736c617415d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_bcaf83f7-6882-454e-b7d4-5726b5c3457b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_bcaf83f7-6882-454e-b7d4-5726b5c3457b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_bde0c9d4-8a98-4945-af80-b1246c1ce9ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_bde0c9d4-8a98-4945-af80-b1246c1ce9ed" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_a2ff98ad-32fe-4884-b462-49c98af914ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_a2ff98ad-32fe-4884-b462-49c98af914ac" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_36872e9b-6c1a-40dc-bdcb-2c715deac1b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2e121359-2e37-464c-8b98-81ea70aa7526" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_36872e9b-6c1a-40dc-bdcb-2c715deac1b2" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StockPlansAvailableforGrantDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#StockPlansAvailableforGrantDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StockPlansAvailableforGrantDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0ba487d2-e170-443a-80de-202b6bbe26d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7fbc4aef-1903-4b1f-8bd9-5e74a9f3308b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0ba487d2-e170-443a-80de-202b6bbe26d0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7fbc4aef-1903-4b1f-8bd9-5e74a9f3308b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_200dda29-5c52-47cb-90fa-a9dd83fc04b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7fbc4aef-1903-4b1f-8bd9-5e74a9f3308b" xlink:to="loc_us-gaap_PlanNameAxis_200dda29-5c52-47cb-90fa-a9dd83fc04b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_200dda29-5c52-47cb-90fa-a9dd83fc04b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_200dda29-5c52-47cb-90fa-a9dd83fc04b7" xlink:to="loc_us-gaap_PlanNameDomain_200dda29-5c52-47cb-90fa-a9dd83fc04b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_70dadf1c-38cd-49f5-aac4-d5bf0ce55254" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_200dda29-5c52-47cb-90fa-a9dd83fc04b7" xlink:to="loc_us-gaap_PlanNameDomain_70dadf1c-38cd-49f5-aac4-d5bf0ce55254" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_A2021PlanMember_03f171b5-de68-4c05-8f69-9613bde77f5d" xlink:href="npce-20251231.xsd#npce_A2021PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_70dadf1c-38cd-49f5-aac4-d5bf0ce55254" xlink:to="loc_npce_A2021PlanMember_03f171b5-de68-4c05-8f69-9613bde77f5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:href="npce-20251231.xsd#npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0ba487d2-e170-443a-80de-202b6bbe26d0" xlink:to="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_c94c5661-18b8-497b-b94c-65c1978b3d62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_c94c5661-18b8-497b-b94c-65c1978b3d62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_7a99a5a2-c7ad-48d0-ae73-b6821cfc5051" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_7a99a5a2-c7ad-48d0-ae73-b6821cfc5051" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesGrantedDuringPeriod_705977ac-c5f2-4f9e-97ab-e64555a6b9fa" xlink:href="npce-20251231.xsd#npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesGrantedDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:to="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesGrantedDuringPeriod_705977ac-c5f2-4f9e-97ab-e64555a6b9fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesCanceledDuringPeriod_6f5399f7-535a-4329-a031-03d681d89217" xlink:href="npce-20251231.xsd#npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesCanceledDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:to="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesCanceledDuringPeriod_6f5399f7-535a-4329-a031-03d681d89217" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesWithheldForTaxes_2f46b6be-4734-46e2-918c-f2da5b4a86bf" xlink:href="npce-20251231.xsd#npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesWithheldForTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAvailableForGrantRollForward_f635942a-9345-4e67-8ee1-e245c2e94bf6" xlink:to="loc_npce_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesWithheldForTaxes_2f46b6be-4734-46e2-918c-f2da5b4a86bf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_ea1de528-6329-4906-84bb-12e5b0da057c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StockPlansEmployeeStockOptionsDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#StockPlansEmployeeStockOptionsDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StockPlansEmployeeStockOptionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_77c2ce90-9a7b-4340-b4c3-a680f199df7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_77c2ce90-9a7b-4340-b4c3-a680f199df7b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_b32e2ea6-af64-46be-bb34-47311d844683" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_77c2ce90-9a7b-4340-b4c3-a680f199df7b" xlink:to="loc_us-gaap_PlanNameAxis_b32e2ea6-af64-46be-bb34-47311d844683" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_b32e2ea6-af64-46be-bb34-47311d844683_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_b32e2ea6-af64-46be-bb34-47311d844683" xlink:to="loc_us-gaap_PlanNameDomain_b32e2ea6-af64-46be-bb34-47311d844683_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_e23d8e08-fb57-4b78-b966-2adba5f88b20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_b32e2ea6-af64-46be-bb34-47311d844683" xlink:to="loc_us-gaap_PlanNameDomain_e23d8e08-fb57-4b78-b966-2adba5f88b20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_A2021EmployeeStockPurchasePlanMember_8f1932f0-3fe4-4105-afda-afe3072a0f2d" xlink:href="npce-20251231.xsd#npce_A2021EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_e23d8e08-fb57-4b78-b966-2adba5f88b20" xlink:to="loc_npce_A2021EmployeeStockPurchasePlanMember_8f1932f0-3fe4-4105-afda-afe3072a0f2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_eeba081e-5d3f-4b67-a7ae-739ad09c6a35" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_77c2ce90-9a7b-4340-b4c3-a680f199df7b" xlink:to="loc_srt_RangeAxis_eeba081e-5d3f-4b67-a7ae-739ad09c6a35" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_eeba081e-5d3f-4b67-a7ae-739ad09c6a35_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_eeba081e-5d3f-4b67-a7ae-739ad09c6a35" xlink:to="loc_srt_RangeMember_eeba081e-5d3f-4b67-a7ae-739ad09c6a35_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ddbf6700-8ef6-4a35-9251-523225ad98c4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_eeba081e-5d3f-4b67-a7ae-739ad09c6a35" xlink:to="loc_srt_RangeMember_ddbf6700-8ef6-4a35-9251-523225ad98c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_016ba06b-0f3a-4b5a-863c-b28560584d50" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ddbf6700-8ef6-4a35-9251-523225ad98c4" xlink:to="loc_srt_MinimumMember_016ba06b-0f3a-4b5a-863c-b28560584d50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_76f4614d-77c8-4c45-a037-332298b56d54" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ddbf6700-8ef6-4a35-9251-523225ad98c4" xlink:to="loc_srt_MaximumMember_76f4614d-77c8-4c45-a037-332298b56d54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019b3092-ca2d-72bb-a657-05d54bcdb60f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_77c2ce90-9a7b-4340-b4c3-a680f199df7b" xlink:to="loc_us-gaap_AwardTypeAxis_019b3092-ca2d-72bb-a657-05d54bcdb60f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019b3092-ca2d-72bb-a657-05d54bcdb60f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019b3092-ca2d-72bb-a657-05d54bcdb60f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019b3092-ca2d-72bb-a657-05d54bcdb60f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019b3092-ca2d-76a0-957d-23ae74da4db8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019b3092-ca2d-72bb-a657-05d54bcdb60f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019b3092-ca2d-76a0-957d-23ae74da4db8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019b3092-eb29-785d-9bc8-ba45967c2761" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019b3092-ca2d-76a0-957d-23ae74da4db8" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019b3092-eb29-785d-9bc8-ba45967c2761" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_1b0d8704-36f9-45c0-9fe5-0c025ffa12ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_1b0d8704-36f9-45c0-9fe5-0c025ffa12ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_20eed3d7-b2d1-4a0e-8dae-6c75b2ca7dc0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_20eed3d7-b2d1-4a0e-8dae-6c75b2ca7dc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_201cc42e-ed10-4227-acb8-a1191c82b671" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_201cc42e-ed10-4227-acb8-a1191c82b671" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_ee337ed5-87ed-4cec-8dd6-59f3ec38f5f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_ee337ed5-87ed-4cec-8dd6-59f3ec38f5f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_afd6931a-5d8f-4d77-a162-29adb31a9395" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_afd6931a-5d8f-4d77-a162-29adb31a9395" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_ab89e399-1842-429f-b7a0-bc3f4afe9f76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_ab89e399-1842-429f-b7a0-bc3f4afe9f76" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_4b02846e-2dd8-44e6-980c-c027c955d2b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1028995f-36a4-4364-bfa1-a3b65838bb0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_4b02846e-2dd8-44e6-980c-c027c955d2b9" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StockPlansRestrictedStockUnitsDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#StockPlansRestrictedStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StockPlansRestrictedStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8e0e7b38-5711-4ea4-ade4-fd7ad4a52196" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e21bfc53-deae-44e6-b71c-c4448bb59331" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8e0e7b38-5711-4ea4-ade4-fd7ad4a52196" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e21bfc53-deae-44e6-b71c-c4448bb59331" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_724ceec8-8373-4da7-884e-01422e589be7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e21bfc53-deae-44e6-b71c-c4448bb59331" xlink:to="loc_us-gaap_AwardTypeAxis_724ceec8-8373-4da7-884e-01422e589be7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_724ceec8-8373-4da7-884e-01422e589be7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_724ceec8-8373-4da7-884e-01422e589be7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_724ceec8-8373-4da7-884e-01422e589be7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f9cc9e0-b814-4242-8ab1-de5b4c398984" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_724ceec8-8373-4da7-884e-01422e589be7" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f9cc9e0-b814-4242-8ab1-de5b4c398984" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_3a1efa23-f940-4910-acd6-32e1781f016a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f9cc9e0-b814-4242-8ab1-de5b4c398984" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_3a1efa23-f940-4910-acd6-32e1781f016a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_29f08f7d-50ca-4793-b968-e745272d3ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8e0e7b38-5711-4ea4-ade4-fd7ad4a52196" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_29f08f7d-50ca-4793-b968-e745272d3ff3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_eed2366a-babf-4ae7-b9d1-b991b3b83704" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_29f08f7d-50ca-4793-b968-e745272d3ff3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_eed2366a-babf-4ae7-b9d1-b991b3b83704" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0ffa177d-463b-4190-a288-751ac709d881" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_29f08f7d-50ca-4793-b968-e745272d3ff3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0ffa177d-463b-4190-a288-751ac709d881" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_779a1633-7cad-4f04-a946-587c21386f82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_29f08f7d-50ca-4793-b968-e745272d3ff3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_779a1633-7cad-4f04-a946-587c21386f82" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_2123a95e-2b5a-4080-a3cf-acba4ad9d3c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_29f08f7d-50ca-4793-b968-e745272d3ff3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_2123a95e-2b5a-4080-a3cf-acba4ad9d3c0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_b1127322-2d6f-4525-8994-d6215296c029" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c6071c64-4948-4e1b-b08a-4e1995be20b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_8e0e7b38-5711-4ea4-ade4-fd7ad4a52196" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c6071c64-4948-4e1b-b08a-4e1995be20b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_f2f42ac5-99a7-43cd-8a49-6adbfa156fc5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c6071c64-4948-4e1b-b08a-4e1995be20b4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_f2f42ac5-99a7-43cd-8a49-6adbfa156fc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_b04ecca9-4c08-403e-b209-255559133b63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c6071c64-4948-4e1b-b08a-4e1995be20b4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_b04ecca9-4c08-403e-b209-255559133b63" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_067bafdc-2a2a-4515-a5cf-d44b1ddd088c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c6071c64-4948-4e1b-b08a-4e1995be20b4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_067bafdc-2a2a-4515-a5cf-d44b1ddd088c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_07548afa-703b-4729-bfb1-52caef88fad2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c6071c64-4948-4e1b-b08a-4e1995be20b4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_07548afa-703b-4729-bfb1-52caef88fad2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_af754e82-a025-4a48-a545-2d73793b8e48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/StockPlansRecognizedStockbasedCompensationDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#StockPlansRecognizedStockbasedCompensationDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/StockPlansRecognizedStockbasedCompensationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7c6eeb16-e95a-4b3f-a05b-278b1d95217a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_157ed772-b377-453e-95f9-80f6cddcba78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7c6eeb16-e95a-4b3f-a05b-278b1d95217a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_157ed772-b377-453e-95f9-80f6cddcba78" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_5e9654d6-2ae1-43ac-ba0e-9bf6a0098f0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_157ed772-b377-453e-95f9-80f6cddcba78" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_5e9654d6-2ae1-43ac-ba0e-9bf6a0098f0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_5e9654d6-2ae1-43ac-ba0e-9bf6a0098f0c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5e9654d6-2ae1-43ac-ba0e-9bf6a0098f0c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_5e9654d6-2ae1-43ac-ba0e-9bf6a0098f0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_502624e1-5b85-4434-94c5-752125628561" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5e9654d6-2ae1-43ac-ba0e-9bf6a0098f0c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_502624e1-5b85-4434-94c5-752125628561" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_82402a42-4c08-49d2-b97f-fc2bc29739f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_502624e1-5b85-4434-94c5-752125628561" xlink:to="loc_us-gaap_CostOfSalesMember_82402a42-4c08-49d2-b97f-fc2bc29739f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_SalesAndMarketingMember_019bb1e0-6deb-7e16-ba4e-efb5b5046168" xlink:href="npce-20251231.xsd#npce_SalesAndMarketingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_502624e1-5b85-4434-94c5-752125628561" xlink:to="loc_npce_SalesAndMarketingMember_019bb1e0-6deb-7e16-ba4e-efb5b5046168" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_64e4de06-8360-400b-90f2-1d0ff3b49265" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_502624e1-5b85-4434-94c5-752125628561" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_64e4de06-8360-400b-90f2-1d0ff3b49265" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_5b97aa5a-fcb8-46b0-82be-89b821101d74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_502624e1-5b85-4434-94c5-752125628561" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_5b97aa5a-fcb8-46b0-82be-89b821101d74" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_651befc0-9874-4513-be8a-abe3f8830427" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_157ed772-b377-453e-95f9-80f6cddcba78" xlink:to="loc_us-gaap_AwardTypeAxis_651befc0-9874-4513-be8a-abe3f8830427" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_651befc0-9874-4513-be8a-abe3f8830427_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_651befc0-9874-4513-be8a-abe3f8830427" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_651befc0-9874-4513-be8a-abe3f8830427_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_19c62c52-9e5f-4a8e-ae8b-6c91dddaad2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_651befc0-9874-4513-be8a-abe3f8830427" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_19c62c52-9e5f-4a8e-ae8b-6c91dddaad2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_StockOptionsAndRestrictedStockUnitsMember_bd2f7015-8322-48e2-99c9-50d3f38bd82d" xlink:href="npce-20251231.xsd#npce_StockOptionsAndRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_19c62c52-9e5f-4a8e-ae8b-6c91dddaad2a" xlink:to="loc_npce_StockOptionsAndRestrictedStockUnitsMember_bd2f7015-8322-48e2-99c9-50d3f38bd82d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_5273b55c-4280-4044-bf6b-38a532d573b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_19c62c52-9e5f-4a8e-ae8b-6c91dddaad2a" xlink:to="loc_us-gaap_EmployeeStockMember_5273b55c-4280-4044-bf6b-38a532d573b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_107516bd-2029-4e78-87f9-8d45c6eb2ae4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7c6eeb16-e95a-4b3f-a05b-278b1d95217a" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_107516bd-2029-4e78-87f9-8d45c6eb2ae4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/IncomeTaxesAdditionalInformationDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#IncomeTaxesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/IncomeTaxesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLossCarryforwardsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_e4af75fc-ecc2-498e-ad33-8876ac7a213b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLossCarryforwardsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_e4af75fc-ecc2-498e-ad33-8876ac7a213b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_dbab5439-451a-454e-9caf-aa6aff795c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_e4af75fc-ecc2-498e-ad33-8876ac7a213b" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_dbab5439-451a-454e-9caf-aa6aff795c6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_dbab5439-451a-454e-9caf-aa6aff795c6f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_dbab5439-451a-454e-9caf-aa6aff795c6f" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_dbab5439-451a-454e-9caf-aa6aff795c6f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_9a9b62e7-4516-4e40-80ce-50464cdcc266" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_dbab5439-451a-454e-9caf-aa6aff795c6f" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_9a9b62e7-4516-4e40-80ce-50464cdcc266" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticCountryMember_d04d3786-6d4e-4861-b495-9bb3be368f14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DomesticCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_9a9b62e7-4516-4e40-80ce-50464cdcc266" xlink:to="loc_us-gaap_DomesticCountryMember_d04d3786-6d4e-4861-b495-9bb3be368f14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_d3968936-d0a4-4197-9b45-ba034c7d64b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_9a9b62e7-4516-4e40-80ce-50464cdcc266" xlink:to="loc_us-gaap_ForeignCountryMember_d3968936-d0a4-4197-9b45-ba034c7d64b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_b9b12944-4ee4-4ccc-811d-fe9134f5e7ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StateAndLocalJurisdictionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_9a9b62e7-4516-4e40-80ce-50464cdcc266" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_b9b12944-4ee4-4ccc-811d-fe9134f5e7ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodAxis_cf8a6c02-62be-40bc-b421-ae6799c8d347" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_e4af75fc-ecc2-498e-ad33-8876ac7a213b" xlink:to="loc_us-gaap_TaxPeriodAxis_cf8a6c02-62be-40bc-b421-ae6799c8d347" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_cf8a6c02-62be-40bc-b421-ae6799c8d347_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_cf8a6c02-62be-40bc-b421-ae6799c8d347" xlink:to="loc_us-gaap_TaxPeriodDomain_cf8a6c02-62be-40bc-b421-ae6799c8d347_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_5d4af4ac-61f2-481d-b7ee-27b9b083e077" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_cf8a6c02-62be-40bc-b421-ae6799c8d347" xlink:to="loc_us-gaap_TaxPeriodDomain_5d4af4ac-61f2-481d-b7ee-27b9b083e077" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxYear2025Member_019c8be6-e8ac-72f9-bda9-6181a38680b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxYear2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_5d4af4ac-61f2-481d-b7ee-27b9b083e077" xlink:to="loc_us-gaap_TaxYear2025Member_019c8be6-e8ac-72f9-bda9-6181a38680b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxYear2024Member_91d54955-a59b-4996-ae2b-ba97cc68793d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxYear2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_5d4af4ac-61f2-481d-b7ee-27b9b083e077" xlink:to="loc_us-gaap_TaxYear2024Member_91d54955-a59b-4996-ae2b-ba97cc68793d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardAxis_2d2db844-9508-45b5-a939-973a62114225" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxCreditCarryforwardAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_e4af75fc-ecc2-498e-ad33-8876ac7a213b" xlink:to="loc_us-gaap_TaxCreditCarryforwardAxis_2d2db844-9508-45b5-a939-973a62114225" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardNameDomain_2d2db844-9508-45b5-a939-973a62114225_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxCreditCarryforwardNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxCreditCarryforwardAxis_2d2db844-9508-45b5-a939-973a62114225" xlink:to="loc_us-gaap_TaxCreditCarryforwardNameDomain_2d2db844-9508-45b5-a939-973a62114225_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardNameDomain_f56fa9c2-40cd-4402-95d6-c5dbc9da3c5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxCreditCarryforwardNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxCreditCarryforwardAxis_2d2db844-9508-45b5-a939-973a62114225" xlink:to="loc_us-gaap_TaxCreditCarryforwardNameDomain_f56fa9c2-40cd-4402-95d6-c5dbc9da3c5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchMember_d260a139-0200-4d57-943e-fbb847b9d336" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardNameDomain_f56fa9c2-40cd-4402-95d6-c5dbc9da3c5c" xlink:to="loc_us-gaap_ResearchMember_d260a139-0200-4d57-943e-fbb847b9d336" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortizationPeriod_9b35e5a1-e40f-4e4a-b5a4-b1417dcae386" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostAmortizationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_CapitalizedContractCostAmortizationPeriod_9b35e5a1-e40f-4e4a-b5a4-b1417dcae386" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_c6eb610b-d146-4a1e-bff6-36d539ff7e1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_c6eb610b-d146-4a1e-bff6-36d539ff7e1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_ValuationAllowanceDeferredTaxLiabilitiesIncreaseDecreaseAmount_a4007b3b-7f56-4fa5-aac0-95b169665558" xlink:href="npce-20251231.xsd#npce_ValuationAllowanceDeferredTaxLiabilitiesIncreaseDecreaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_npce_ValuationAllowanceDeferredTaxLiabilitiesIncreaseDecreaseAmount_a4007b3b-7f56-4fa5-aac0-95b169665558" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_1d6c75dd-a894-412a-8c7a-8141aa841e75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_OperatingLossCarryforwards_1d6c75dd-a894-412a-8c7a-8141aa841e75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsNotSubjectToExpiration_019c7067-b9b3-716c-8e78-2be278b849f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsNotSubjectToExpiration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsNotSubjectToExpiration_019c7067-b9b3-716c-8e78-2be278b849f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardAmount_6dc166c6-df1a-45ce-9642-59df90496fb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxCreditCarryforwardAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_TaxCreditCarryforwardAmount_6dc166c6-df1a-45ce-9642-59df90496fb9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_npce_OperatingLossCarryforwardsAmountPermanentlyLimited_30d0e532-1721-4a63-859d-5e3c68139ad2" xlink:href="npce-20251231.xsd#npce_OperatingLossCarryforwardsAmountPermanentlyLimited"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_npce_OperatingLossCarryforwardsAmountPermanentlyLimited_30d0e532-1721-4a63-859d-5e3c68139ad2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_ca465f9b-7286-4d76-bc19-3a8dee4597a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_e40d4c76-6deb-47c7-aa91-655f4b117e47" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_ca465f9b-7286-4d76-bc19-3a8dee4597a3" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/NetLossperShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesOutstandingDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#NetLossperShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/NetLossperShareAttributabletoCommonStockholdersPotentiallyDilutiveSecuritiesOutstandingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_dbe2ff87-a0c0-45f3-85dc-76cb6c393e30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4a1c0ba0-b53f-4d06-9488-953e3350f2ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_dbe2ff87-a0c0-45f3-85dc-76cb6c393e30" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4a1c0ba0-b53f-4d06-9488-953e3350f2ab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_13ead2a4-245e-40c9-ac72-7600df7eacb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_4a1c0ba0-b53f-4d06-9488-953e3350f2ab" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_13ead2a4-245e-40c9-ac72-7600df7eacb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_13ead2a4-245e-40c9-ac72-7600df7eacb9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_13ead2a4-245e-40c9-ac72-7600df7eacb9" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_13ead2a4-245e-40c9-ac72-7600df7eacb9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0b17ffa7-e43c-4238-9523-aee222486156" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_13ead2a4-245e-40c9-ac72-7600df7eacb9" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0b17ffa7-e43c-4238-9523-aee222486156" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_49eaa0f2-cb2b-4b61-82fe-b25d9f668354" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0b17ffa7-e43c-4238-9523-aee222486156" xlink:to="loc_us-gaap_EmployeeStockOptionMember_49eaa0f2-cb2b-4b61-82fe-b25d9f668354" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_0f4294f8-fc64-435c-82ac-a62659513f36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0b17ffa7-e43c-4238-9523-aee222486156" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_0f4294f8-fc64-435c-82ac-a62659513f36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_ddcb9afe-1396-4b83-942b-7733ea07dfa2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0b17ffa7-e43c-4238-9523-aee222486156" xlink:to="loc_us-gaap_EmployeeStockMember_ddcb9afe-1396-4b83-942b-7733ea07dfa2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_25d7b45f-ce16-43e7-806e-6bd51407d971" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_dbe2ff87-a0c0-45f3-85dc-76cb6c393e30" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_25d7b45f-ce16-43e7-806e-6bd51407d971" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.neuropace.com/role/SegmentInformationAdditionalInformationDetails" xlink:type="simple" xlink:href="npce-20251231.xsd#SegmentInformationAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.neuropace.com/role/SegmentInformationAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a39a5ce-e8a4-4047-92ae-0d6fd32ed5a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EntityWideRevenueMajorCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_b36ff43f-682d-4b2e-b46c-24e39a54e328" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a39a5ce-e8a4-4047-92ae-0d6fd32ed5a5" xlink:to="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_b36ff43f-682d-4b2e-b46c-24e39a54e328" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_ef153d3c-b8ee-4063-be04-117ce234b0ce" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideRevenueByMajorCustomersByReportingSegmentsTable_b36ff43f-682d-4b2e-b46c-24e39a54e328" xlink:to="loc_srt_StatementGeographicalAxis_ef153d3c-b8ee-4063-be04-117ce234b0ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_ef153d3c-b8ee-4063-be04-117ce234b0ce_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_ef153d3c-b8ee-4063-be04-117ce234b0ce" xlink:to="loc_srt_SegmentGeographicalDomain_ef153d3c-b8ee-4063-be04-117ce234b0ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_1b343bfb-4a38-468f-9808-33a9409467ab" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_ef153d3c-b8ee-4063-be04-117ce234b0ce" xlink:to="loc_srt_SegmentGeographicalDomain_1b343bfb-4a38-468f-9808-33a9409467ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_8c8eb8f1-591f-46df-90dc-39ad02203792" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_1b343bfb-4a38-468f-9808-33a9409467ab" xlink:to="loc_us-gaap_NonUsMember_8c8eb8f1-591f-46df-90dc-39ad02203792" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_53280b8f-ed74-4845-9705-311b7a4ed253" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a39a5ce-e8a4-4047-92ae-0d6fd32ed5a5" xlink:to="loc_us-gaap_NumberOfOperatingSegments_53280b8f-ed74-4845-9705-311b7a4ed253" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_93665056-8865-4bd0-8d3f-7a18ed47d041" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a39a5ce-e8a4-4047-92ae-0d6fd32ed5a5" xlink:to="loc_us-gaap_NumberOfReportableSegments_93665056-8865-4bd0-8d3f-7a18ed47d041" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a3fb6a22-68cf-40af-ac7d-5ae0f7337b6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideRevenueMajorCustomerLineItems_4a39a5ce-e8a4-4047-92ae-0d6fd32ed5a5" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a3fb6a22-68cf-40af-ac7d-5ae0f7337b6b" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
