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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019cb95f-e79c-7248-b589-006ae5f3f9bf,g:edc52dd9-1aef-4b05-8cae-9e991f4bd8c6-->
<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.msasafety.com/role/CondensedConsolidatedStatementsofChangesinRetainedEarningsAccumulatedOtherComprehensiveLoss" xlink:type="simple" xlink:href="msa-20260331.xsd#CondensedConsolidatedStatementsofChangesinRetainedEarningsAccumulatedOtherComprehensiveLoss"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/CondensedConsolidatedStatementsofChangesinRetainedEarningsAccumulatedOtherComprehensiveLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019cb95f-e8f5-789f-80c8-6cb34341e382" 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_019cb95f-e8f5-7677-ab91-e1f90b87a0be" 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_019cb95f-e8f5-789f-80c8-6cb34341e382" xlink:to="loc_us-gaap_StatementTable_019cb95f-e8f5-7677-ab91-e1f90b87a0be" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-7d88-ab11-62ba2ba12e50" 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_019cb95f-e8f5-7677-ab91-e1f90b87a0be" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-7d88-ab11-62ba2ba12e50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7d88-ab11-62ba2ba12e50_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_019cb95f-e8f5-7d88-ab11-62ba2ba12e50" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7d88-ab11-62ba2ba12e50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7258-8f75-65174a29a253" 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_019cb95f-e8f5-7d88-ab11-62ba2ba12e50" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7258-8f75-65174a29a253" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019cb95f-e8f5-7896-8d41-06b3dc679163" 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_019cb95f-e8f5-7258-8f75-65174a29a253" xlink:to="loc_us-gaap_RetainedEarningsMember_019cb95f-e8f5-7896-8d41-06b3dc679163" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019cb95f-e8f5-7f95-ad0c-f03da34f1ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7258-8f75-65174a29a253" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019cb95f-e8f5-7f95-ad0c-f03da34f1ba1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" 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_019cb95f-e8f5-789f-80c8-6cb34341e382" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019cb95f-e8f5-7a53-b2a2-c0eac106684b" 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_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_StockholdersEquity_019cb95f-e8f5-7a53-b2a2-c0eac106684b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019cb95f-e8f5-7668-b1d7-eee8dc173dc7" 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_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_NetIncomeLoss_019cb95f-e8f5-7668-b1d7-eee8dc173dc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019cb95f-e8f5-7bc1-aa80-f80bc3d905bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019cb95f-e8f5-7bc1-aa80-f80bc3d905bc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019cb95f-e8f5-7956-8f01-c1b720ccd372" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_019cb95f-e8f5-7956-8f01-c1b720ccd372" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019dbb8b-319a-76e7-a43c-3d7ea6d723a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019dbb8b-319a-76e7-a43c-3d7ea6d723a2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockStock_019cb95f-e8f5-7520-898f-d9420871e2de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStockStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_DividendsCommonStockStock_019cb95f-e8f5-7520-898f-d9420871e2de" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPreferredStockStock_019cb95f-e8f5-7974-a813-dfec493aa5c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsPreferredStockStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019cb95f-e8f5-71b3-9dac-ee6dbc4b9ab2" xlink:to="loc_us-gaap_DividendsPreferredStockStock_019cb95f-e8f5-7974-a813-dfec493aa5c1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019cb95f-e8f5-77ca-b155-04a9dc4b455b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/RevenueRecognitionDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#RevenueRecognitionDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/RevenueRecognitionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019cb95f-e8f5-7c89-b067-25460712ad1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019cb95f-e8f5-7c89-b067-25460712ad1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019cb95f-e8f5-775a-8858-ec51d2a292be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019cb95f-e8f5-7c89-b067-25460712ad1e" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019cb95f-e8f5-775a-8858-ec51d2a292be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019cb95f-e8f5-7fd9-bf2c-ff75240d515e" 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_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019cb95f-e8f5-7fd9-bf2c-ff75240d515e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019cb95f-e8f5-779d-bf75-9285dfc56fdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019cb95f-e8f5-779d-bf75-9285dfc56fdb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/RevenueRecognitionDetails_1" xlink:type="simple" xlink:href="msa-20260331.xsd#RevenueRecognitionDetails_1"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/RevenueRecognitionDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019cb95f-e8f5-7c89-b067-25460712ad1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019cb95f-e8f5-7c89-b067-25460712ad1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019cb95f-e8f5-7fd9-bf2c-ff75240d515e" 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_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019cb95f-e8f5-7fd9-bf2c-ff75240d515e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019cb95f-e8f5-779d-bf75-9285dfc56fdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019cb95f-e8f5-76dc-882c-ac27a26f66fd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019cb95f-e8f5-779d-bf75-9285dfc56fdb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/RestructuringChargesAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#RestructuringChargesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/RestructuringChargesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_019cb95f-e8f5-7266-8a87-b3c8bfad53e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-7260-a79b-93f1c95ba253" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019cb95f-e8f5-7266-8a87-b3c8bfad53e8" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-7260-a79b-93f1c95ba253" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7efc-b6af-c56fe66078e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-7260-a79b-93f1c95ba253" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7efc-b6af-c56fe66078e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7efc-b6af-c56fe66078e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7efc-b6af-c56fe66078e4" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7efc-b6af-c56fe66078e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7443-9160-e02440892669" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7efc-b6af-c56fe66078e4" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7443-9160-e02440892669" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AmericasSegmentMember_019cb95f-e8f5-7c2b-912d-036ba06428e0" xlink:href="msa-20260331.xsd#msa_AmericasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7443-9160-e02440892669" xlink:to="loc_msa_AmericasSegmentMember_019cb95f-e8f5-7c2b-912d-036ba06428e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_InternationalMember_019cb95f-e8f5-77f5-95a8-6f63fd622d7a" xlink:href="msa-20260331.xsd#msa_InternationalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7443-9160-e02440892669" xlink:to="loc_msa_InternationalMember_019cb95f-e8f5-77f5-95a8-6f63fd622d7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7780-a63c-0e15c761abb4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-7260-a79b-93f1c95ba253" xlink:to="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7780-a63c-0e15c761abb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7780-a63c-0e15c761abb4_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7780-a63c-0e15c761abb4" xlink:to="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7780-a63c-0e15c761abb4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c43-835d-48caaf41c773" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7780-a63c-0e15c761abb4" xlink:to="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c43-835d-48caaf41c773" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019cb95f-e8f5-7910-9f8e-77882fbad844" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c43-835d-48caaf41c773" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019cb95f-e8f5-7910-9f8e-77882fbad844" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019cb95f-e8f5-7261-ae68-59c2beb9d262" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c43-835d-48caaf41c773" xlink:to="loc_us-gaap_OperatingSegmentsMember_019cb95f-e8f5-7261-ae68-59c2beb9d262" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_019cb95f-e8f5-7e0f-b50e-c9e3fdddc05f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019cb95f-e8f5-7266-8a87-b3c8bfad53e8" xlink:to="loc_us-gaap_RestructuringCharges_019cb95f-e8f5-7e0f-b50e-c9e3fdddc05f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/RestructuringChargesActivityandReserveBalanceforRestructuringChargesbySegmentDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#RestructuringChargesActivityandReserveBalanceforRestructuringChargesbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/RestructuringChargesActivityandReserveBalanceforRestructuringChargesbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_019cb95f-e8f5-77d0-9728-9b4be4b05f7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-774b-9250-bc053924976e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019cb95f-e8f5-77d0-9728-9b4be4b05f7e" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-774b-9250-bc053924976e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7dd3-8042-4cbef4f89580" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-774b-9250-bc053924976e" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7dd3-8042-4cbef4f89580" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7dd3-8042-4cbef4f89580_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7dd3-8042-4cbef4f89580" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7dd3-8042-4cbef4f89580_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7d71-a7da-045ea6004d6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7dd3-8042-4cbef4f89580" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7d71-a7da-045ea6004d6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AmericasSegmentMember_019cb95f-e8f5-7a37-a7b8-57dba88de2ea" xlink:href="msa-20260331.xsd#msa_AmericasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7d71-a7da-045ea6004d6e" xlink:to="loc_msa_AmericasSegmentMember_019cb95f-e8f5-7a37-a7b8-57dba88de2ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_InternationalMember_019cb95f-e8f5-7220-b69c-cda705b37374" xlink:href="msa-20260331.xsd#msa_InternationalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7d71-a7da-045ea6004d6e" xlink:to="loc_msa_InternationalMember_019cb95f-e8f5-7220-b69c-cda705b37374" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-79c3-aa24-73dab8a58a47" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019cb95f-e8f5-774b-9250-bc053924976e" xlink:to="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-79c3-aa24-73dab8a58a47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-79c3-aa24-73dab8a58a47_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-79c3-aa24-73dab8a58a47" xlink:to="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-79c3-aa24-73dab8a58a47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c94-b673-54a13c595e76" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-79c3-aa24-73dab8a58a47" xlink:to="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c94-b673-54a13c595e76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019cb95f-e8f5-73aa-8868-c475150e36c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c94-b673-54a13c595e76" xlink:to="loc_us-gaap_OperatingSegmentsMember_019cb95f-e8f5-73aa-8868-c475150e36c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019cb95f-e8f5-7c3e-8d6e-d36d6e68ea6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7c94-b673-54a13c595e76" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019cb95f-e8f5-7c3e-8d6e-d36d6e68ea6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringReserveRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019cb95f-e8f5-77d0-9728-9b4be4b05f7e" xlink:to="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_019cb95f-e8f5-79e6-81b0-d0e86393b10c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:to="loc_us-gaap_RestructuringReserve_019cb95f-e8f5-79e6-81b0-d0e86393b10c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_RestructuringChargesbeforeAdjustments_019cb95f-e8f5-7bc1-9fd9-3ab572294711" xlink:href="msa-20260331.xsd#msa_RestructuringChargesbeforeAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:to="loc_msa_RestructuringChargesbeforeAdjustments_019cb95f-e8f5-7bc1-9fd9-3ab572294711" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_RestructuringChargesReversalOfCost_019cb95f-e8f5-7270-b744-73b98e92bbad" xlink:href="msa-20260331.xsd#msa_RestructuringChargesReversalOfCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:to="loc_msa_RestructuringChargesReversalOfCost_019cb95f-e8f5-7270-b744-73b98e92bbad" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveTranslationAdjustment_019cb95f-e8f5-7b6b-8168-d9892ce0f6d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringReserveTranslationAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:to="loc_us-gaap_RestructuringReserveTranslationAdjustment_019cb95f-e8f5-7b6b-8168-d9892ce0f6d1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_019cb95f-e8f5-78b5-9296-49e4aeb76ccd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_019cb95f-e8f5-7e25-becc-466934541aab" xlink:to="loc_us-gaap_PaymentsForRestructuring_019cb95f-e8f5-78b5-9296-49e4aeb76ccd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_019cb95f-e8f5-7622-8143-82fe6597379f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringReserve"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/PropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#PropertyPlantandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/PropertyPlantandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019cb95f-e8f5-7d65-9f01-bbb5fab75157" 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_019cb95f-e8f5-788c-9cb5-e8b7089f0857" 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_019cb95f-e8f5-7d65-9f01-bbb5fab75157" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019cb95f-e8f5-788c-9cb5-e8b7089f0857" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019cb95f-e8f5-7aa3-9034-c756ee03b017" 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_019cb95f-e8f5-788c-9cb5-e8b7089f0857" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019cb95f-e8f5-7aa3-9034-c756ee03b017" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7aa3-9034-c756ee03b017_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_019cb95f-e8f5-7aa3-9034-c756ee03b017" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7aa3-9034-c756ee03b017_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7e26-9b15-dff98835f5c2" 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_019cb95f-e8f5-7aa3-9034-c756ee03b017" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7e26-9b15-dff98835f5c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_019cb95f-e8f5-7447-8590-f970a536a51c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7e26-9b15-dff98835f5c2" xlink:to="loc_us-gaap_LandMember_019cb95f-e8f5-7447-8590-f970a536a51c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingMember_019cb95f-e8f5-7383-8530-f0a5cb4b3241" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7e26-9b15-dff98835f5c2" xlink:to="loc_us-gaap_BuildingMember_019cb95f-e8f5-7383-8530-f0a5cb4b3241" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_019cb95f-e8f5-718a-bb17-b21e2808b982" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7e26-9b15-dff98835f5c2" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_019cb95f-e8f5-718a-bb17-b21e2808b982" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_019cb95f-e8f5-74ba-ba5d-373f9fcb923e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019cb95f-e8f5-7e26-9b15-dff98835f5c2" xlink:to="loc_us-gaap_ConstructionInProgressMember_019cb95f-e8f5-74ba-ba5d-373f9fcb923e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019cb95f-e8f5-7938-81a1-0e27c40d109e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019cb95f-e8f5-7d65-9f01-bbb5fab75157" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019cb95f-e8f5-7938-81a1-0e27c40d109e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019cb95f-e8f5-7eb1-a927-e14d1eff1ea1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019cb95f-e8f5-7d65-9f01-bbb5fab75157" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019cb95f-e8f5-7eb1-a927-e14d1eff1ea1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019cb95f-e8f5-7caf-9934-94c62a3546da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019cb95f-e8f5-7d65-9f01-bbb5fab75157" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019cb95f-e8f5-7caf-9934-94c62a3546da" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/ReclassificationsOutofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#ReclassificationsOutofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/ReclassificationsOutofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019cb95f-e8f5-7659-b473-a043af40f2e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019cb95f-e8f5-761f-b7e9-5a2c9c8dd5aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019cb95f-e8f5-7659-b473-a043af40f2e7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019cb95f-e8f5-761f-b7e9-5a2c9c8dd5aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-72f0-8d8e-e18d78461ad4" 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_AccumulatedOtherComprehensiveIncomeLossTable_019cb95f-e8f5-761f-b7e9-5a2c9c8dd5aa" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-72f0-8d8e-e18d78461ad4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72f0-8d8e-e18d78461ad4_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_019cb95f-e8f5-72f0-8d8e-e18d78461ad4" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72f0-8d8e-e18d78461ad4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72c7-9f0f-dcda27327fb5" 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_019cb95f-e8f5-72f0-8d8e-e18d78461ad4" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72c7-9f0f-dcda27327fb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019cb95f-e8f5-7f69-bd31-d8e44c5ee14d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72c7-9f0f-dcda27327fb5" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019cb95f-e8f5-7f69-bd31-d8e44c5ee14d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_019cb95f-e8f5-7970-9338-59ad995125ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019cb95f-e8f5-7f69-bd31-d8e44c5ee14d" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_019cb95f-e8f5-7970-9338-59ad995125ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_019cb95f-e8f5-7481-83f4-6de7936141e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019cb95f-e8f5-7f69-bd31-d8e44c5ee14d" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_019cb95f-e8f5-7481-83f4-6de7936141e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019d646b-dcf3-7535-b673-62e19454d38c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72c7-9f0f-dcda27327fb5" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_019d646b-dcf3-7535-b673-62e19454d38c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019cb95f-e8f5-7848-8c24-46e3d3ee4216" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-72c7-9f0f-dcda27327fb5" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019cb95f-e8f5-7848-8c24-46e3d3ee4216" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019cb95f-e8f5-7659-b473-a043af40f2e7" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019cb95f-e8f5-7fef-bb86-9ec1c65f21bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019cb95f-e8f5-7fef-bb86-9ec1c65f21bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_019cb95f-e8f5-7636-8409-930d6d9f8356" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_019cb95f-e8f5-7636-8409-930d6d9f8356" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019cb95f-e8f5-7180-80ac-8a84f839c45d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_019cb95f-e8f5-7180-80ac-8a84f839c45d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_019cb95f-e8f5-7381-9e24-9b80b59bb2d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_019cb95f-e8f5-7381-9e24-9b80b59bb2d1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cb95f-e8f5-76ad-8755-ee6aa22bc576" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019cb95f-e8f5-7c29-aae2-20127f2909c5" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019cb95f-e8f5-76ad-8755-ee6aa22bc576" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019cb95f-e8f5-7f5e-97f0-388f6bf99db7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/CapitalStockNarrativeDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#CapitalStockNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/CapitalStockNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalUnitLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCapitalUnitsTable_019cb95f-e8f5-7e13-a15a-32dafce555f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfCapitalUnitsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_ScheduleOfCapitalUnitsTable_019cb95f-e8f5-7e13-a15a-32dafce555f3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019cb95f-e8f5-77e5-8adb-6738deb3f200" 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_ScheduleOfCapitalUnitsTable_019cb95f-e8f5-7e13-a15a-32dafce555f3" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019cb95f-e8f5-77e5-8adb-6738deb3f200" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-77e5-8adb-6738deb3f200_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_019cb95f-e8f5-77e5-8adb-6738deb3f200" xlink:to="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-77e5-8adb-6738deb3f200_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-7e08-8703-58ce7288b8d8" 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_019cb95f-e8f5-77e5-8adb-6738deb3f200" xlink:to="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-7e08-8703-58ce7288b8d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CumulativePreferredStockMember_019cb95f-e8f5-7c37-892f-1776a88f3909" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CumulativePreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-7e08-8703-58ce7288b8d8" xlink:to="loc_us-gaap_CumulativePreferredStockMember_019cb95f-e8f5-7c37-892f-1776a88f3909" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SecondCumulativePreferredVotingStockMember_019cb95f-e8f5-725c-91bc-4fa7fa3db6ad" xlink:href="msa-20260331.xsd#msa_SecondCumulativePreferredVotingStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-7e08-8703-58ce7288b8d8" xlink:to="loc_msa_SecondCumulativePreferredVotingStockMember_019cb95f-e8f5-725c-91bc-4fa7fa3db6ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019cb95f-e8f5-7f3d-b543-ee723603979c" 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_ClassOfStockDomain_019cb95f-e8f5-7e08-8703-58ce7288b8d8" xlink:to="loc_us-gaap_CommonStockMember_019cb95f-e8f5-7f3d-b543-ee723603979c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019cb95f-e8f5-74b0-b389-117805aca72e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019cb95f-e8f5-7e08-8703-58ce7288b8d8" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019cb95f-e8f5-74b0-b389-117805aca72e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-7ec5-ab94-ef6e6c5188f3" 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_ScheduleOfCapitalUnitsTable_019cb95f-e8f5-7e13-a15a-32dafce555f3" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-7ec5-ab94-ef6e6c5188f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7ec5-ab94-ef6e6c5188f3_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_019cb95f-e8f5-7ec5-ab94-ef6e6c5188f3" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7ec5-ab94-ef6e6c5188f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7e13-8f07-fc658fdb7752" 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_019cb95f-e8f5-7ec5-ab94-ef6e6c5188f3" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7e13-8f07-fc658fdb7752" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019cb95f-e8f5-7bf2-964e-8d346c31f7a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7e13-8f07-fc658fdb7752" xlink:to="loc_us-gaap_PreferredStockMember_019cb95f-e8f5-7bf2-964e-8d346c31f7a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_019cb95f-e8f5-7eb0-9fb0-0275cd49c813" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_019cb95f-e8f5-7eb0-9fb0-0275cd49c813" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019cb95f-e8f5-7b4d-96f5-63bc2fc17d49" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019cb95f-e8f5-7b4d-96f5-63bc2fc17d49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_019cb95f-e8f5-7d7d-a0b5-cd42d55fbe27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_019cb95f-e8f5-7d7d-a0b5-cd42d55fbe27" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockRedemptionPricePerShare_019cb95f-e8f5-789c-a126-e68f6ff21e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockRedemptionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_PreferredStockRedemptionPricePerShare_019cb95f-e8f5-789c-a126-e68f6ff21e5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019cb95f-e8f5-73fd-82d5-c36a9b52d41b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019cb95f-e8f5-73fd-82d5-c36a9b52d41b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockPreferredShares_019cb95f-e8f5-7c8c-a1c4-9b1d3513bcc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockPreferredShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_TreasuryStockPreferredShares_019cb95f-e8f5-7c8c-a1c4-9b1d3513bcc8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_019cb95f-e8f5-7193-b881-f5caffb74c61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_TreasuryStockValue_019cb95f-e8f5-7193-b881-f5caffb74c61" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019cb95f-e8f5-78a9-870a-e118dc851e4d" 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_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019cb95f-e8f5-78a9-870a-e118dc851e4d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019cb95f-e8f5-7d69-9a1a-c1b5f61b1ace" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019cb95f-e8f5-7d69-9a1a-c1b5f61b1ace" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019cb95f-e8f5-7629-9229-2f3379047111" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_CommonStockSharesIssued_019cb95f-e8f5-7629-9229-2f3379047111" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019cb95f-e8f5-7185-8e11-727680f1c86b" 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_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019cb95f-e8f5-7185-8e11-727680f1c86b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019cb95f-e8f5-7adf-9b32-0210f6aba2a5" 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_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019cb95f-e8f5-7adf-9b32-0210f6aba2a5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019cb95f-e8f5-7adb-951c-83b31b7f5ead" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019cb95f-e8f5-7adb-951c-83b31b7f5ead" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_019cb95f-e8f5-7704-8d89-2ac82f716bee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_TreasuryStockCommonShares_019cb95f-e8f5-7704-8d89-2ac82f716bee" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross_019cb95f-e8f5-75c3-9a81-507e327404d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_019cb95f-e8f5-7d35-a3a5-c4508d9f3db9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross_019cb95f-e8f5-75c3-9a81-507e327404d8" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/CapitalStockScheduleofCommonStockActivityDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#CapitalStockScheduleofCommonStockActivityDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/CapitalStockScheduleofCommonStockActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019cb95f-e8f5-74b7-9a1a-0de23e5d8f0c" 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_019cb95f-e8f5-7cde-9442-fc09401f76b9" 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_019cb95f-e8f5-74b7-9a1a-0de23e5d8f0c" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019cb95f-e8f5-7cde-9442-fc09401f76b9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019cb95f-e8f5-70d8-ab28-32349af4c550" 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_ScheduleOfStockByClassTable_019cb95f-e8f5-7cde-9442-fc09401f76b9" xlink:to="loc_us-gaap_AwardTypeAxis_019cb95f-e8f5-70d8-ab28-32349af4c550" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-70d8-ab28-32349af4c550_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_019cb95f-e8f5-70d8-ab28-32349af4c550" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-70d8-ab28-32349af4c550_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7e2c-8f05-a47715029623" 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_019cb95f-e8f5-70d8-ab28-32349af4c550" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7e2c-8f05-a47715029623" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_RestrictedAndPerformanceStockAwardsMember_019cb95f-e8f5-79f0-ac5e-0e76cd5cdf78" xlink:href="msa-20260331.xsd#msa_RestrictedAndPerformanceStockAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7e2c-8f05-a47715029623" xlink:to="loc_msa_RestrictedAndPerformanceStockAwardsMember_019cb95f-e8f5-79f0-ac5e-0e76cd5cdf78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019cb95f-e8f5-75d5-9fc3-a51b517d58fa" 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_019cb95f-e8f5-7e2c-8f05-a47715029623" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019cb95f-e8f5-75d5-9fc3-a51b517d58fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_019cb95f-e8f5-7743-b0f1-ab081377dd67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7e2c-8f05-a47715029623" xlink:to="loc_us-gaap_StockCompensationPlanMember_019cb95f-e8f5-7743-b0f1-ab081377dd67" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_ShareRepurchaseProgramMember_019cb95f-e8f5-7874-8fe6-e59be73dd792" xlink:href="msa-20260331.xsd#msa_ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7e2c-8f05-a47715029623" xlink:to="loc_msa_ShareRepurchaseProgramMember_019cb95f-e8f5-7874-8fe6-e59be73dd792" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-7f65-bb94-54acad194e9e" 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_ScheduleOfStockByClassTable_019cb95f-e8f5-7cde-9442-fc09401f76b9" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019cb95f-e8f5-7f65-bb94-54acad194e9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7f65-bb94-54acad194e9e_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_019cb95f-e8f5-7f65-bb94-54acad194e9e" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-7f65-bb94-54acad194e9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-76dc-928f-b9978a20eafb" 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_019cb95f-e8f5-7f65-bb94-54acad194e9e" xlink:to="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-76dc-928f-b9978a20eafb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019cb95f-e8f5-7b3f-9016-ed562bfd7a24" 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_019cb95f-e8f5-76dc-928f-b9978a20eafb" xlink:to="loc_us-gaap_CommonStockMember_019cb95f-e8f5-7b3f-9016-ed562bfd7a24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019cb95f-e8f5-7427-9cf7-c7fa3918f303" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019cb95f-e8f5-76dc-928f-b9978a20eafb" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019cb95f-e8f5-7427-9cf7-c7fa3918f303" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_CommonStockActivityRollForward_019cb95f-e8f5-7171-bb30-188d15458b6f" xlink:href="msa-20260331.xsd#msa_CommonStockActivityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019cb95f-e8f5-74b7-9a1a-0de23e5d8f0c" xlink:to="loc_msa_CommonStockActivityRollForward_019cb95f-e8f5-7171-bb30-188d15458b6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019cb95f-e8f5-7bae-8113-72705daeef8e" 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_msa_CommonStockActivityRollForward_019cb95f-e8f5-7171-bb30-188d15458b6f" xlink:to="loc_us-gaap_StockholdersEquity_019cb95f-e8f5-7bae-8113-72705daeef8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019cb95f-e8f5-7fe5-aa7f-33ab3bdae754" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_msa_CommonStockActivityRollForward_019cb95f-e8f5-7171-bb30-188d15458b6f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019cb95f-e8f5-7fe5-aa7f-33ab3bdae754" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross_019cb95f-e8f5-70d3-9cfd-3c1ff3965d50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_msa_CommonStockActivityRollForward_019cb95f-e8f5-7171-bb30-188d15458b6f" xlink:to="loc_us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross_019cb95f-e8f5-70d3-9cfd-3c1ff3965d50" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019cb95f-e8f5-71e3-9f73-cab92585e781" 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_msa_CommonStockActivityRollForward_019cb95f-e8f5-7171-bb30-188d15458b6f" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019cb95f-e8f5-71e3-9f73-cab92585e781" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019cb95f-e8f5-75c5-b981-fce45fb77261" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/SegmentInformationScheduleOfReportableSegmentInformationDetail" xlink:type="simple" xlink:href="msa-20260331.xsd#SegmentInformationScheduleOfReportableSegmentInformationDetail"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/SegmentInformationScheduleOfReportableSegmentInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019cb95f-e8f5-7c68-afe7-f596acc27a2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019cb95f-e8f5-7c68-afe7-f596acc27a2c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7ea4-bc27-4747569dffa0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019cb95f-e8f5-7c68-afe7-f596acc27a2c" xlink:to="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7ea4-bc27-4747569dffa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7ea4-bc27-4747569dffa0_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7ea4-bc27-4747569dffa0" xlink:to="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7ea4-bc27-4747569dffa0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7785-9219-e6e580e6d30e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019cb95f-e8f5-7ea4-bc27-4747569dffa0" xlink:to="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7785-9219-e6e580e6d30e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019cb95f-e8f5-778d-a66f-4dc7c9b4cdf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7785-9219-e6e580e6d30e" xlink:to="loc_us-gaap_OperatingSegmentsMember_019cb95f-e8f5-778d-a66f-4dc7c9b4cdf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019cb95f-e8f5-7f4c-a375-a83b0fd47c77" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019cb95f-e8f5-7785-9219-e6e580e6d30e" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019cb95f-e8f5-7f4c-a375-a83b0fd47c77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7750-891c-70d7e64edaf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019cb95f-e8f5-7c68-afe7-f596acc27a2c" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7750-891c-70d7e64edaf1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7750-891c-70d7e64edaf1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7750-891c-70d7e64edaf1" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7750-891c-70d7e64edaf1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-766b-9aa2-526a2fe9b5ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-7750-891c-70d7e64edaf1" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-766b-9aa2-526a2fe9b5ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AmericasSegmentMember_019cb95f-e8f5-7b11-999e-ace272c776dc" xlink:href="msa-20260331.xsd#msa_AmericasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-766b-9aa2-526a2fe9b5ff" xlink:to="loc_msa_AmericasSegmentMember_019cb95f-e8f5-7b11-999e-ace272c776dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_InternationalSegmentMember_019cb95f-e8f5-78bd-83f1-a4e7d874a138" xlink:href="msa-20260331.xsd#msa_InternationalSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-766b-9aa2-526a2fe9b5ff" xlink:to="loc_msa_InternationalSegmentMember_019cb95f-e8f5-78bd-83f1-a4e7d874a138" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019cb95f-e8f5-788b-b2b2-d1ae63415d62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_Revenues_019cb95f-e8f5-788b-b2b2-d1ae63415d62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019cb95f-e8f5-7aec-af7a-0c729f7ded5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019cb95f-e8f5-7aec-af7a-0c729f7ded5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019cb95f-e8f5-7f8d-92bf-604c40cc1106" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019cb95f-e8f5-7f8d-92bf-604c40cc1106" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019cb95f-e8f5-7608-9690-8c77c16a3461" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019cb95f-e8f5-7608-9690-8c77c16a3461" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_OperatingIncomeLossAdjusted_019cb95f-e8f5-7b8f-b81a-146cf343626f" xlink:href="msa-20260331.xsd#msa_OperatingIncomeLossAdjusted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_msa_OperatingIncomeLossAdjusted_019cb95f-e8f5-7b8f-b81a-146cf343626f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019cb95f-e8f5-74b8-9d97-89d482a44d70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019cb95f-e8f5-74b8-9d97-89d482a44d70" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionExpense_019cb95f-e8f5-74fd-a927-25447103aa76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_PensionExpense_019cb95f-e8f5-74fd-a927-25447103aa76" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019cb95f-e8f5-7e80-a3be-f3d889b9f9f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_Assets_019cb95f-e8f5-7e80-a3be-f3d889b9f9f6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_019cb95f-e8f5-7410-8645-18304c2d1bdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019cb95f-e8f5-7861-aefb-a68242535dbf" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_019cb95f-e8f5-7410-8645-18304c2d1bdb" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/SegmentInformationPercentageofTotalSalesbyProductGroupDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#SegmentInformationPercentageofTotalSalesbyProductGroupDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/SegmentInformationPercentageofTotalSalesbyProductGroupDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_019cb95f-e8f5-77de-8876-471008403684" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019cb95f-e8f5-7c4f-b99e-31118ff73f56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_019cb95f-e8f5-77de-8876-471008403684" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019cb95f-e8f5-7c4f-b99e-31118ff73f56" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-742d-9f65-fe334837b3fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019cb95f-e8f5-7c4f-b99e-31118ff73f56" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-742d-9f65-fe334837b3fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-742d-9f65-fe334837b3fe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-742d-9f65-fe334837b3fe" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-742d-9f65-fe334837b3fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7741-ab78-4072bf876746" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e8f5-742d-9f65-fe334837b3fe" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7741-ab78-4072bf876746" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AmericasSegmentMember_019cb95f-e8f5-79e5-9637-93b9b776ff5f" xlink:href="msa-20260331.xsd#msa_AmericasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7741-ab78-4072bf876746" xlink:to="loc_msa_AmericasSegmentMember_019cb95f-e8f5-79e5-9637-93b9b776ff5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_InternationalMember_019cb95f-e8f5-7ff7-bc60-aee60e68384b" xlink:href="msa-20260331.xsd#msa_InternationalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e8f5-7741-ab78-4072bf876746" xlink:to="loc_msa_InternationalMember_019cb95f-e8f5-7ff7-bc60-aee60e68384b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019cb95f-e8f5-7599-ae82-05f377f1cee8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019cb95f-e8f5-7c4f-b99e-31118ff73f56" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019cb95f-e8f5-7599-ae82-05f377f1cee8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019cb95f-e8f5-7599-ae82-05f377f1cee8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019cb95f-e8f5-7599-ae82-05f377f1cee8" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019cb95f-e8f5-7599-ae82-05f377f1cee8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019cb95f-e8f5-72e1-bf45-4dbc6f2a4134" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019cb95f-e8f5-7599-ae82-05f377f1cee8" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019cb95f-e8f5-72e1-bf45-4dbc6f2a4134" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_019cb95f-e8f5-710c-b851-d145590d049e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019cb95f-e8f5-72e1-bf45-4dbc6f2a4134" xlink:to="loc_us-gaap_SalesRevenueNetMember_019cb95f-e8f5-710c-b851-d145590d049e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesMember_019d20ab-af53-793a-b4a3-e7e11e6556a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019cb95f-e8f5-72e1-bf45-4dbc6f2a4134" xlink:to="loc_us-gaap_SalesMember_019d20ab-af53-793a-b4a3-e7e11e6556a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019cb95f-e8f5-77af-9113-704a876bfc70" 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_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019cb95f-e8f5-7c4f-b99e-31118ff73f56" xlink:to="loc_srt_ProductOrServiceAxis_019cb95f-e8f5-77af-9113-704a876bfc70" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-77af-9113-704a876bfc70_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_019cb95f-e8f5-77af-9113-704a876bfc70" xlink:to="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-77af-9113-704a876bfc70_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-79ec-add0-efbfd08d10c9" 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_019cb95f-e8f5-77af-9113-704a876bfc70" xlink:to="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-79ec-add0-efbfd08d10c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DetectionMember_019d20a9-0be4-7e97-bca7-bcc27b706df6" xlink:href="msa-20260331.xsd#msa_DetectionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-79ec-add0-efbfd08d10c9" xlink:to="loc_msa_DetectionMember_019d20a9-0be4-7e97-bca7-bcc27b706df6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_FireServiceMember_019d86fa-ebe1-7b9e-8a39-709bd0e2510a" xlink:href="msa-20260331.xsd#msa_FireServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-79ec-add0-efbfd08d10c9" xlink:to="loc_msa_FireServiceMember_019d86fa-ebe1-7b9e-8a39-709bd0e2510a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_IndustrialPPEAndOtherMember_019d20ab-af53-7f06-97f3-5e1170ca6ab0" xlink:href="msa-20260331.xsd#msa_IndustrialPPEAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019cb95f-e8f5-79ec-add0-efbfd08d10c9" xlink:to="loc_msa_IndustrialPPEAndOtherMember_019d20ab-af53-7f06-97f3-5e1170ca6ab0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019cb95f-e8f5-74d7-8971-4d3b46a08946" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019cb95f-e8f5-7c4f-b99e-31118ff73f56" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019cb95f-e8f5-74d7-8971-4d3b46a08946" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019cb95f-e8f5-74d7-8971-4d3b46a08946_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019cb95f-e8f5-74d7-8971-4d3b46a08946" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019cb95f-e8f5-74d7-8971-4d3b46a08946_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019cb95f-e8f5-71dc-8518-15304fd6f260" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019cb95f-e8f5-74d7-8971-4d3b46a08946" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019cb95f-e8f5-71dc-8518-15304fd6f260" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductConcentrationRiskMember_019cb95f-e8f5-7853-8d7d-c0f6f161aab4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019cb95f-e8f5-71dc-8518-15304fd6f260" xlink:to="loc_us-gaap_ProductConcentrationRiskMember_019cb95f-e8f5-7853-8d7d-c0f6f161aab4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019cb95f-e8f5-7c32-8de5-5b4b2e3a663d" 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_EntityWideInformationRevenueFromExternalCustomerLineItems_019cb95f-e8f5-77de-8876-471008403684" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019cb95f-e8f5-7c32-8de5-5b4b2e3a663d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019cb95f-e8f5-7d1e-a3e5-19969fc16219" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_019cb95f-e8f5-77de-8876-471008403684" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019cb95f-e8f5-7d1e-a3e5-19969fc16219" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/StockPlansSummaryofRestrictedStockandUnitActivityDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#StockPlansSummaryofRestrictedStockandUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/StockPlansSummaryofRestrictedStockandUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e8f5-7cee-93ab-acd2ec7c5379" 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_019cb95f-e8f5-78b6-a4ec-8d8cf6a4da94" 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_019cb95f-e8f5-7cee-93ab-acd2ec7c5379" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb95f-e8f5-78b6-a4ec-8d8cf6a4da94" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019cb95f-e8f5-7dfb-b766-49b9dbc3dcf5" 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_019cb95f-e8f5-78b6-a4ec-8d8cf6a4da94" xlink:to="loc_us-gaap_AwardTypeAxis_019cb95f-e8f5-7dfb-b766-49b9dbc3dcf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7dfb-b766-49b9dbc3dcf5_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_019cb95f-e8f5-7dfb-b766-49b9dbc3dcf5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7dfb-b766-49b9dbc3dcf5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7df5-86e7-8955834808ce" 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_019cb95f-e8f5-7dfb-b766-49b9dbc3dcf5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7df5-86e7-8955834808ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019cb95f-e8f5-7054-9d94-f79e4025d52a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e8f5-7df5-86e7-8955834808ce" xlink:to="loc_us-gaap_RestrictedStockMember_019cb95f-e8f5-7054-9d94-f79e4025d52a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019cb95f-e8f5-7e4e-bea2-0a8b0d1aaf77" 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_019cb95f-e8f5-7cee-93ab-acd2ec7c5379" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019cb95f-e8f5-7e4e-bea2-0a8b0d1aaf77" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019cb95f-e8f5-7d9d-9c4e-5a1dbca148ef" 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_019cb95f-e8f5-7e4e-bea2-0a8b0d1aaf77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019cb95f-e8f5-7d9d-9c4e-5a1dbca148ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019cb95f-e8f5-7fa6-9f0a-bd1636da7bf1" 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_019cb95f-e8f5-7e4e-bea2-0a8b0d1aaf77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019cb95f-e8f5-7fa6-9f0a-bd1636da7bf1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019cb95f-e8f5-743b-97e7-65a4de707aa3" 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_019cb95f-e8f5-7e4e-bea2-0a8b0d1aaf77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019cb95f-e8f5-743b-97e7-65a4de707aa3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019cb95f-e8f5-7009-9e14-389f21f298eb" 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_019cb95f-e8f5-7e4e-bea2-0a8b0d1aaf77" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019cb95f-e8f5-7009-9e14-389f21f298eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019cb95f-e8f5-7b8e-ba8f-0c84cc2d9d1d" 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_019cb95f-e9a6-7a53-bbe2-bf75d9be623a" 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_019cb95f-e8f5-7cee-93ab-acd2ec7c5379" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019cb95f-e9a6-7a53-bbe2-bf75d9be623a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019cb95f-e9a6-74e2-81ed-b468d98d2c98" 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_019cb95f-e9a6-7a53-bbe2-bf75d9be623a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019cb95f-e9a6-74e2-81ed-b468d98d2c98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7a2b-b78a-df804072e67b" 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_019cb95f-e9a6-7a53-bbe2-bf75d9be623a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7a2b-b78a-df804072e67b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7a6f-8330-000179aec9d5" 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_019cb95f-e9a6-7a53-bbe2-bf75d9be623a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7a6f-8330-000179aec9d5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019cb95f-e9a6-74c5-83fe-769ef4f78585" 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_019cb95f-e9a6-7a53-bbe2-bf75d9be623a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019cb95f-e9a6-74c5-83fe-769ef4f78585" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019cb95f-e9a6-7b93-9330-be07768c4453" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/StockPlansAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#StockPlansAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/StockPlansAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7526-b66f-7f4a0f5d5ea5" 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_019cb95f-e9a6-7b50-a271-8959744b3c0c" 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_019cb95f-e9a6-7526-b66f-7f4a0f5d5ea5" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb95f-e9a6-7b50-a271-8959744b3c0c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019cb95f-e9a6-7047-8e9f-97d14c6107a9" 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_019cb95f-e9a6-7b50-a271-8959744b3c0c" xlink:to="loc_us-gaap_AwardTypeAxis_019cb95f-e9a6-7047-8e9f-97d14c6107a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7047-8e9f-97d14c6107a9_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_019cb95f-e9a6-7047-8e9f-97d14c6107a9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7047-8e9f-97d14c6107a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7408-bbf8-6c20708c79de" 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_019cb95f-e9a6-7047-8e9f-97d14c6107a9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7408-bbf8-6c20708c79de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019cb95f-e9a6-7e0e-9ff2-a54ac2bca451" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7408-bbf8-6c20708c79de" xlink:to="loc_us-gaap_PerformanceSharesMember_019cb95f-e9a6-7e0e-9ff2-a54ac2bca451" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019cb95f-e9a6-7fc4-8ec8-a6c31217976e" 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_019cb95f-e9a6-7b50-a271-8959744b3c0c" xlink:to="loc_srt_RangeAxis_019cb95f-e9a6-7fc4-8ec8-a6c31217976e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019cb95f-e9a6-7fc4-8ec8-a6c31217976e_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_019cb95f-e9a6-7fc4-8ec8-a6c31217976e" xlink:to="loc_srt_RangeMember_019cb95f-e9a6-7fc4-8ec8-a6c31217976e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019cb95f-e9a6-742b-aaf7-29db78860666" 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_019cb95f-e9a6-7fc4-8ec8-a6c31217976e" xlink:to="loc_srt_RangeMember_019cb95f-e9a6-742b-aaf7-29db78860666" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019cb95f-e9a6-7d24-b00f-7709bb86fafe" 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_019cb95f-e9a6-742b-aaf7-29db78860666" xlink:to="loc_srt_MinimumMember_019cb95f-e9a6-7d24-b00f-7709bb86fafe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019cb95f-e9a6-76d3-b592-6df1d187b87c" 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_019cb95f-e9a6-742b-aaf7-29db78860666" xlink:to="loc_srt_MaximumMember_019cb95f-e9a6-76d3-b592-6df1d187b87c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_019cb95f-e9a6-7251-95a1-f6dfd3906f30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7526-b66f-7f4a0f5d5ea5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_019cb95f-e9a6-7251-95a1-f6dfd3906f30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_PercentageOfTargetAwardBasedOnAchievingTargetedTotalShareholderReturnBasedOnWhichFinalNumberOfSharesToBeIssuedForPerformanceStockUnits_019cb95f-e9a6-7f61-ab32-b4e9cad6dce7" xlink:href="msa-20260331.xsd#msa_PercentageOfTargetAwardBasedOnAchievingTargetedTotalShareholderReturnBasedOnWhichFinalNumberOfSharesToBeIssuedForPerformanceStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7526-b66f-7f4a0f5d5ea5" xlink:to="loc_msa_PercentageOfTargetAwardBasedOnAchievingTargetedTotalShareholderReturnBasedOnWhichFinalNumberOfSharesToBeIssuedForPerformanceStockUnits_019cb95f-e9a6-7f61-ab32-b4e9cad6dce7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SharebasedCompensationArrangementbySharebasePaymentAwardFairValueAssumptionsAverageClosingPriceUsedtoCalculateExpectedDividendRatePeriod_019cb95f-e9a6-739d-93ff-bc9d749cbc5a" xlink:href="msa-20260331.xsd#msa_SharebasedCompensationArrangementbySharebasePaymentAwardFairValueAssumptionsAverageClosingPriceUsedtoCalculateExpectedDividendRatePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7526-b66f-7f4a0f5d5ea5" xlink:to="loc_msa_SharebasedCompensationArrangementbySharebasePaymentAwardFairValueAssumptionsAverageClosingPriceUsedtoCalculateExpectedDividendRatePeriod_019cb95f-e9a6-739d-93ff-bc9d749cbc5a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SharebasedCompensationArrangementbySharebasePaymentAwardFairValueAssumptionsStockBetaDailyPriceDataPeriod_019cb95f-e9a6-7cb5-817a-2ce77ac789b2" xlink:href="msa-20260331.xsd#msa_SharebasedCompensationArrangementbySharebasePaymentAwardFairValueAssumptionsStockBetaDailyPriceDataPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7526-b66f-7f4a0f5d5ea5" xlink:to="loc_msa_SharebasedCompensationArrangementbySharebasePaymentAwardFairValueAssumptionsStockBetaDailyPriceDataPeriod_019cb95f-e9a6-7cb5-817a-2ce77ac789b2" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/StockPlansWeightedAverageRiskAssumptionsDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#StockPlansWeightedAverageRiskAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/StockPlansWeightedAverageRiskAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7f18-a324-19028aea0bae" 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_019cb95f-e9a6-7160-9308-ab798a5a77a1" 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_019cb95f-e9a6-7f18-a324-19028aea0bae" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb95f-e9a6-7160-9308-ab798a5a77a1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019cb95f-e9a6-7090-a1d8-508cdc0882aa" 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_019cb95f-e9a6-7160-9308-ab798a5a77a1" xlink:to="loc_us-gaap_AwardTypeAxis_019cb95f-e9a6-7090-a1d8-508cdc0882aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7090-a1d8-508cdc0882aa_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_019cb95f-e9a6-7090-a1d8-508cdc0882aa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7090-a1d8-508cdc0882aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7053-8d08-69c86da779df" 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_019cb95f-e9a6-7090-a1d8-508cdc0882aa" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7053-8d08-69c86da779df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019cb95f-e9a6-7fed-9a5e-a5d306bb7943" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7053-8d08-69c86da779df" xlink:to="loc_us-gaap_PerformanceSharesMember_019cb95f-e9a6-7fed-9a5e-a5d306bb7943" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis_019cb95f-e9a6-71e6-86bd-2c195b92d9aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb95f-e9a6-7160-9308-ab798a5a77a1" xlink:to="loc_us-gaap_ValuationTechniqueAxis_019cb95f-e9a6-71e6-86bd-2c195b92d9aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019cb95f-e9a6-71e6-86bd-2c195b92d9aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019cb95f-e9a6-71e6-86bd-2c195b92d9aa" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019cb95f-e9a6-71e6-86bd-2c195b92d9aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019cb95f-e9a6-75fd-b315-3686cf89d0ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019cb95f-e9a6-71e6-86bd-2c195b92d9aa" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019cb95f-e9a6-75fd-b315-3686cf89d0ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MonteCarloApproachMember_019cb95f-e9a6-7fe8-9d93-0967d326cc2e" xlink:href="msa-20260331.xsd#msa_MonteCarloApproachMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019cb95f-e9a6-75fd-b315-3686cf89d0ab" xlink:to="loc_msa_MonteCarloApproachMember_019cb95f-e9a6-7fe8-9d93-0967d326cc2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7718-a321-510cfcc4c350" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7f18-a324-19028aea0bae" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7718-a321-510cfcc4c350" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_019cb95f-e9a6-76d6-8025-730e99b8f567" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7f18-a324-19028aea0bae" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_019cb95f-e9a6-76d6-8025-730e99b8f567" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_019cb95f-e9a6-7091-9eb3-eb725eac0b52" 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_019cb95f-e9a6-7f18-a324-19028aea0bae" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_019cb95f-e9a6-7091-9eb3-eb725eac0b52" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_019cb95f-e9a6-7c1c-877c-054372678662" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7f18-a324-19028aea0bae" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_019cb95f-e9a6-7c1c-877c-054372678662" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsStockBeta_019cb95f-e9a6-7a47-8dde-1d1d0e64288b" xlink:href="msa-20260331.xsd#msa_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsStockBeta"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-7f18-a324-19028aea0bae" xlink:to="loc_msa_SharebasedCompensationArrangementbySharebasedPaymentAwardFairValueAssumptionsStockBeta_019cb95f-e9a6-7a47-8dde-1d1d0e64288b" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/StockPlansSummaryofPerformanceStockUnitActivityDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#StockPlansSummaryofPerformanceStockUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/StockPlansSummaryofPerformanceStockUnitActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-77f4-aff1-6084f7968704" 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_019cb95f-e9a6-7b87-add8-1a60d952a98e" 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_019cb95f-e9a6-77f4-aff1-6084f7968704" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019cb95f-e9a6-7b87-add8-1a60d952a98e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019cb95f-e9a6-7b8b-8f0d-d6071b508beb" 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_019cb95f-e9a6-7b87-add8-1a60d952a98e" xlink:to="loc_us-gaap_AwardTypeAxis_019cb95f-e9a6-7b8b-8f0d-d6071b508beb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7b8b-8f0d-d6071b508beb_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_019cb95f-e9a6-7b8b-8f0d-d6071b508beb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-7b8b-8f0d-d6071b508beb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-776a-9aef-728c1c5f79e9" 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_019cb95f-e9a6-7b8b-8f0d-d6071b508beb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-776a-9aef-728c1c5f79e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019cb95f-e9a6-74d4-a286-e800b817b004" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019cb95f-e9a6-776a-9aef-728c1c5f79e9" xlink:to="loc_us-gaap_PerformanceSharesMember_019cb95f-e9a6-74d4-a286-e800b817b004" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-77f4-aff1-6084f7968704" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019cb95f-e9a6-73b9-a440-f932468603ac" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019cb95f-e9a6-73b9-a440-f932468603ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019cb95f-e9a6-7fad-b7e3-a089046c6801" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019cb95f-e9a6-7fad-b7e3-a089046c6801" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriod_019cb95f-e9a6-7b0f-8366-847838a34c65" xlink:href="msa-20260331.xsd#msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:to="loc_msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriod_019cb95f-e9a6-7b0f-8366-847838a34c65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019cb95f-e9a6-7b1b-b130-befe423df1c8" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019cb95f-e9a6-7b1b-b130-befe423df1c8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019cb95f-e9a6-7da1-bd0f-2794859f7045" 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_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_019cb95f-e9a6-7008-9af6-13c7aaec1817" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019cb95f-e9a6-7da1-bd0f-2794859f7045" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019cb95f-e9a6-7863-8a4a-daab57f8c53a" 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_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" 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_019cb95f-e9a6-77f4-aff1-6084f7968704" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019cb95f-e9a6-781f-81dd-dc623eac1a8d" 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_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019cb95f-e9a6-781f-81dd-dc623eac1a8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7e8c-888a-7cf2ba4262d7" 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_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-7e8c-888a-7cf2ba4262d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-702b-bfa1-7d57b8747679" xlink:href="msa-20260331.xsd#msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" xlink:to="loc_msa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAdjustmentInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-702b-bfa1-7d57b8747679" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-71c8-be6a-5b63a0e3dad9" 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_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019cb95f-e9a6-71c8-be6a-5b63a0e3dad9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019cb95f-e9a6-78f6-bbca-cf3727e9778b" 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_019cb95f-e9a6-7de1-8f2b-22d1cd5e20bd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019cb95f-e9a6-78f6-bbca-cf3727e9778b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019cb95f-e9a6-7131-89dd-1a454a922a0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_PercentageOfTargetAwardBasedOnAchievingTargetedReturnOnNetAssetsBasedOnWhichFinalNumberOfSharesToBeIssuedForPerformanceStockUnits_019cb95f-e9a6-7e2c-8c0a-4ac6d2615bcf" xlink:href="msa-20260331.xsd#msa_PercentageOfTargetAwardBasedOnAchievingTargetedReturnOnNetAssetsBasedOnWhichFinalNumberOfSharesToBeIssuedForPerformanceStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019cb95f-e9a6-77f4-aff1-6084f7968704" xlink:to="loc_msa_PercentageOfTargetAwardBasedOnAchievingTargetedReturnOnNetAssetsBasedOnWhichFinalNumberOfSharesToBeIssuedForPerformanceStockUnits_019cb95f-e9a6-7e2c-8c0a-4ac6d2615bcf" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/LongTermDebtScheduleofDebtDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#LongTermDebtScheduleofDebtDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/LongTermDebtScheduleofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" 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_019cb95f-e9a6-7bbd-b093-a95732dca0a4" 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_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" xlink:to="loc_us-gaap_DebtInstrumentTable_019cb95f-e9a6-7bbd-b093-a95732dca0a4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019cb95f-e9a6-7e01-8f60-50b88db9f6d6" 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_019cb95f-e9a6-7bbd-b093-a95732dca0a4" xlink:to="loc_us-gaap_DebtInstrumentAxis_019cb95f-e9a6-7e01-8f60-50b88db9f6d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7e01-8f60-50b88db9f6d6_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_019cb95f-e9a6-7e01-8f60-50b88db9f6d6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7e01-8f60-50b88db9f6d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" 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_019cb95f-e9a6-7e01-8f60-50b88db9f6d6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SeniorNotesPayableThroughTwoThousandThirtyOneThreePointFourPercentageMemberMember_019cb95f-e9a6-7b55-9a29-5c925d828da5" xlink:href="msa-20260331.xsd#msa_SeniorNotesPayableThroughTwoThousandThirtyOneThreePointFourPercentageMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" xlink:to="loc_msa_SeniorNotesPayableThroughTwoThousandThirtyOneThreePointFourPercentageMemberMember_019cb95f-e9a6-7b55-9a29-5c925d828da5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MultiCurrencyNoteSeriesCSeniorNotesMember_019cb95f-e9a6-7a76-94e4-505298dc973b" xlink:href="msa-20260331.xsd#msa_MultiCurrencyNoteSeriesCSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" xlink:to="loc_msa_MultiCurrencyNoteSeriesCSeniorNotesMember_019cb95f-e9a6-7a76-94e4-505298dc973b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_NYLNoteFacilitySeriesASeniorNotesMember_019cb95f-e9a6-72e5-83a0-84d20f00eb3a" xlink:href="msa-20260331.xsd#msa_NYLNoteFacilitySeriesASeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" xlink:to="loc_msa_NYLNoteFacilitySeriesASeniorNotesMember_019cb95f-e9a6-72e5-83a0-84d20f00eb3a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019cb95f-e9a6-7235-a321-16c0bf66fa92" 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_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019cb95f-e9a6-7235-a321-16c0bf66fa92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SeniorNotesDue2028Member_019cb95f-e9a6-7463-bc50-3d00332c2d30" xlink:href="msa-20260331.xsd#msa_SeniorNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-73bd-b13c-adfef24d541e" xlink:to="loc_msa_SeniorNotesDue2028Member_019cb95f-e9a6-7463-bc50-3d00332c2d30" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019cb95f-e9a6-7aa4-8a51-b08ff2ded9c4" 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_019cb95f-e9a6-7bbd-b093-a95732dca0a4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019cb95f-e9a6-7aa4-8a51-b08ff2ded9c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7aa4-8a51-b08ff2ded9c4_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_019cb95f-e9a6-7aa4-8a51-b08ff2ded9c4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7aa4-8a51-b08ff2ded9c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7ab0-92ba-a83a7829f1c7" 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_019cb95f-e9a6-7aa4-8a51-b08ff2ded9c4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7ab0-92ba-a83a7829f1c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019cb95f-e9a6-7746-af45-17cf744adcf0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7ab0-92ba-a83a7829f1c7" xlink:to="loc_us-gaap_SeniorNotesMember_019cb95f-e9a6-7746-af45-17cf744adcf0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019cb95f-e9a6-7334-b089-1a59bfaa3f5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7ab0-92ba-a83a7829f1c7" xlink:to="loc_us-gaap_LineOfCreditMember_019cb95f-e9a6-7334-b089-1a59bfaa3f5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019cb95f-e9a6-7981-984d-9e1fc0c2d53d" 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_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019cb95f-e9a6-7981-984d-9e1fc0c2d53d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorLongTermNotes_019cb95f-e9a6-7c41-b723-f3ac8688a7e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorLongTermNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" xlink:to="loc_us-gaap_SeniorLongTermNotes_019cb95f-e9a6-7c41-b723-f3ac8688a7e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019cb95f-e9a6-7724-9b43-a6c3143d1916" 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_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" xlink:to="loc_us-gaap_LongTermDebt_019cb95f-e9a6-7724-9b43-a6c3143d1916" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019cb95f-e9a6-752e-bf76-9b98cfb4a067" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" xlink:to="loc_us-gaap_LongTermDebtCurrent_019cb95f-e9a6-752e-bf76-9b98cfb4a067" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019cb95f-e9a6-75ac-bbd9-9ba2e66815f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7c0e-a8e3-5ad9ec68e32e" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019cb95f-e9a6-75ac-bbd9-9ba2e66815f1" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/LongTermDebtAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#LongTermDebtAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/LongTermDebtAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" 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_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" 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_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_DebtInstrumentTable_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019cb95f-e9a6-762f-b6e4-c84bb1f28b87" 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_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:to="loc_srt_RangeAxis_019cb95f-e9a6-762f-b6e4-c84bb1f28b87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019cb95f-e9a6-762f-b6e4-c84bb1f28b87_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_019cb95f-e9a6-762f-b6e4-c84bb1f28b87" xlink:to="loc_srt_RangeMember_019cb95f-e9a6-762f-b6e4-c84bb1f28b87_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019cb95f-e9a6-773f-be28-5eb3815ed7ed" 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_019cb95f-e9a6-762f-b6e4-c84bb1f28b87" xlink:to="loc_srt_RangeMember_019cb95f-e9a6-773f-be28-5eb3815ed7ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019cb95f-e9a6-7ce3-89b1-2e130e32227b" 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_019cb95f-e9a6-773f-be28-5eb3815ed7ed" xlink:to="loc_srt_MinimumMember_019cb95f-e9a6-7ce3-89b1-2e130e32227b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019cb95f-e9a6-74fe-94c1-88d2582dd120" 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_019cb95f-e9a6-773f-be28-5eb3815ed7ed" xlink:to="loc_srt_MaximumMember_019cb95f-e9a6-74fe-94c1-88d2582dd120" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019cb95f-e9a6-7b21-ae23-8b83e80532de" 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_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:to="loc_us-gaap_VariableRateAxis_019cb95f-e9a6-7b21-ae23-8b83e80532de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019cb95f-e9a6-7b21-ae23-8b83e80532de_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_019cb95f-e9a6-7b21-ae23-8b83e80532de" xlink:to="loc_us-gaap_VariableRateDomain_019cb95f-e9a6-7b21-ae23-8b83e80532de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019cb95f-e9a6-740e-ac55-4f4a676ad9b6" 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_019cb95f-e9a6-7b21-ae23-8b83e80532de" xlink:to="loc_us-gaap_VariableRateDomain_019cb95f-e9a6-740e-ac55-4f4a676ad9b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_OvernightBankFundingRateMember_019cb95f-e9a6-75db-8fc3-235abb5cd9b0" xlink:href="msa-20260331.xsd#msa_OvernightBankFundingRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019cb95f-e9a6-740e-ac55-4f4a676ad9b6" xlink:to="loc_msa_OvernightBankFundingRateMember_019cb95f-e9a6-75db-8fc3-235abb5cd9b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019cb95f-e9a6-7cc3-beb8-1363d761a35c" 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_019cb95f-e9a6-740e-ac55-4f4a676ad9b6" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019cb95f-e9a6-7cc3-beb8-1363d761a35c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019cb95f-e9a6-7694-9e37-944ec25b9f0a" 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_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019cb95f-e9a6-7694-9e37-944ec25b9f0a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7694-9e37-944ec25b9f0a_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_019cb95f-e9a6-7694-9e37-944ec25b9f0a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-7694-9e37-944ec25b9f0a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-73ef-9b08-f50c2686c515" 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_019cb95f-e9a6-7694-9e37-944ec25b9f0a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-73ef-9b08-f50c2686c515" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019cb95f-e9a6-7845-8d36-6571fd91dce0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-73ef-9b08-f50c2686c515" xlink:to="loc_us-gaap_LineOfCreditMember_019cb95f-e9a6-7845-8d36-6571fd91dce0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019cb95f-e9a6-7ae2-975d-5eabfcba1d38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-73ef-9b08-f50c2686c515" xlink:to="loc_us-gaap_SeniorNotesMember_019cb95f-e9a6-7ae2-975d-5eabfcba1d38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019cb95f-e9a6-7096-868d-62a563cd4749" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-73ef-9b08-f50c2686c515" xlink:to="loc_us-gaap_UnsecuredDebtMember_019cb95f-e9a6-7096-868d-62a563cd4749" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_019cb95f-e9a6-7b8b-a467-848f29678330" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019cb95f-e9a6-73ef-9b08-f50c2686c515" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_019cb95f-e9a6-7b8b-a467-848f29678330" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019cb95f-e9a6-7765-a1cf-14122497e896" 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_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:to="loc_us-gaap_DebtInstrumentAxis_019cb95f-e9a6-7765-a1cf-14122497e896" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7765-a1cf-14122497e896_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_019cb95f-e9a6-7765-a1cf-14122497e896" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7765-a1cf-14122497e896_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" 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_019cb95f-e9a6-7765-a1cf-14122497e896" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SeniorRevolvingCreditFacilityMaturingIn2026Member_019cb95f-e9a6-7254-b60b-a3e8d2998b85" xlink:href="msa-20260331.xsd#msa_SeniorRevolvingCreditFacilityMaturingIn2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:to="loc_msa_SeniorRevolvingCreditFacilityMaturingIn2026Member_019cb95f-e9a6-7254-b60b-a3e8d2998b85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MultiCurrencyNoteSeriesCSeniorNotesMember_019cb95f-e9a6-717c-8292-672665da0831" xlink:href="msa-20260331.xsd#msa_MultiCurrencyNoteSeriesCSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:to="loc_msa_MultiCurrencyNoteSeriesCSeniorNotesMember_019cb95f-e9a6-717c-8292-672665da0831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MulticurrencyNotesDuein2031Member_019cb95f-e9a6-77e6-8a88-78dd19b48369" xlink:href="msa-20260331.xsd#msa_MulticurrencyNotesDuein2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:to="loc_msa_MulticurrencyNotesDuein2031Member_019cb95f-e9a6-77e6-8a88-78dd19b48369" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_NYLNoteFacilitySeriesASeniorNotesMember_019cb95f-e9a6-72df-bc65-9bc644716c7c" xlink:href="msa-20260331.xsd#msa_NYLNoteFacilitySeriesASeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:to="loc_msa_NYLNoteFacilitySeriesASeniorNotesMember_019cb95f-e9a6-72df-bc65-9bc644716c7c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_NYLNoteFacilitySeniorUnsecuredNotesMember_019cb95f-e9a6-76cb-ad54-9fe76b2efe25" xlink:href="msa-20260331.xsd#msa_NYLNoteFacilitySeniorUnsecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:to="loc_msa_NYLNoteFacilitySeniorUnsecuredNotesMember_019cb95f-e9a6-76cb-ad54-9fe76b2efe25" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_SeniorNotesDue2028Member_019cb95f-e9a6-7190-9a8c-add1a3b98f8b" xlink:href="msa-20260331.xsd#msa_SeniorNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019cb95f-e9a6-7893-a3ce-446852ae4c4b" xlink:to="loc_msa_SeniorNotesDue2028Member_019cb95f-e9a6-7190-9a8c-add1a3b98f8b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019cb95f-e9a6-73c1-b8f5-27eeaf123ec4" 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_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:to="loc_us-gaap_CreditFacilityAxis_019cb95f-e9a6-73c1-b8f5-27eeaf123ec4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019cb95f-e9a6-73c1-b8f5-27eeaf123ec4_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_019cb95f-e9a6-73c1-b8f5-27eeaf123ec4" xlink:to="loc_us-gaap_CreditFacilityDomain_019cb95f-e9a6-73c1-b8f5-27eeaf123ec4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019cb95f-e9a6-71b5-8b2e-f249fa1a1153" 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_019cb95f-e9a6-73c1-b8f5-27eeaf123ec4" xlink:to="loc_us-gaap_CreditFacilityDomain_019cb95f-e9a6-71b5-8b2e-f249fa1a1153" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_019cb95f-e9a6-72ee-816d-03ba3b80f69d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StandbyLettersOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019cb95f-e9a6-71b5-8b2e-f249fa1a1153" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_019cb95f-e9a6-72ee-816d-03ba3b80f69d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019cb95f-e9a6-73dc-8ed0-f13d58ecd9ed" 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_019cb95f-e9a6-71b5-8b2e-f249fa1a1153" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019cb95f-e9a6-73dc-8ed0-f13d58ecd9ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-709f-bb39-b0b0d3b7f9ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019cb95f-e9a6-7cb2-89ec-0b5754b72cb9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-709f-bb39-b0b0d3b7f9ce" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-709f-bb39-b0b0d3b7f9ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-709f-bb39-b0b0d3b7f9ce" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-709f-bb39-b0b0d3b7f9ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-7ad8-8ef7-af14da8e1d0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-709f-bb39-b0b0d3b7f9ce" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-7ad8-8ef7-af14da8e1d0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MCMember_019cb95f-e9a6-714e-b50b-44b727ff827a" xlink:href="msa-20260331.xsd#msa_MCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-7ad8-8ef7-af14da8e1d0e" xlink:to="loc_msa_MCMember_019cb95f-e9a6-714e-b50b-44b727ff827a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019cb95f-e9a6-7b27-9043-49fa9e819e22" 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_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019cb95f-e9a6-7b27-9043-49fa9e819e22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019cb95f-e9a6-7b74-8b8d-4365b4a44514" 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_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019cb95f-e9a6-7b74-8b8d-4365b4a44514" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DebtInstrumentWeightedAverageRevolverInterestRate_019cb95f-e9a6-7f55-aa34-67089656490d" xlink:href="msa-20260331.xsd#msa_DebtInstrumentWeightedAverageRevolverInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_DebtInstrumentWeightedAverageRevolverInterestRate_019cb95f-e9a6-7f55-aa34-67089656490d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019cb95f-e9a6-756a-8e16-780dff8f09b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019cb95f-e9a6-756a-8e16-780dff8f09b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_LineOfCreditFacilityAccordionFeatureAmount_019cb95f-e9a6-7b1e-932f-b70c972221e8" xlink:href="msa-20260331.xsd#msa_LineOfCreditFacilityAccordionFeatureAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_LineOfCreditFacilityAccordionFeatureAmount_019cb95f-e9a6-7b1e-932f-b70c972221e8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019cb95f-e9a6-7e38-a330-c40252cce114" 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_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019cb95f-e9a6-7e38-a330-c40252cce114" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019cb95f-e9a6-7639-8cca-6ea498c452e1" 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_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019cb95f-e9a6-7639-8cca-6ea498c452e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_019cb95f-e9a6-7dc3-9050-6b04f4aafec5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_LongTermDebtCurrent_019cb95f-e9a6-7dc3-9050-6b04f4aafec5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DebtInstrumentPrincipalAmountDueInYearBeforeMaturity_019cb95f-e9a6-7469-90df-79e73d06f64f" xlink:href="msa-20260331.xsd#msa_DebtInstrumentPrincipalAmountDueInYearBeforeMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_DebtInstrumentPrincipalAmountDueInYearBeforeMaturity_019cb95f-e9a6-7469-90df-79e73d06f64f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DebtInstrumentPrincipalAmountDueAtMaturity_019cb95f-e9a6-7323-80b3-726f63088e31" xlink:href="msa-20260331.xsd#msa_DebtInstrumentPrincipalAmountDueAtMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_DebtInstrumentPrincipalAmountDueAtMaturity_019cb95f-e9a6-7323-80b3-726f63088e31" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DebtInstrumentCovenantFixedChargesCoverageRatioMinimum_019cb95f-e9a6-718a-b51b-03bcc1d33b5b" xlink:href="msa-20260331.xsd#msa_DebtInstrumentCovenantFixedChargesCoverageRatioMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_DebtInstrumentCovenantFixedChargesCoverageRatioMinimum_019cb95f-e9a6-718a-b51b-03bcc1d33b5b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DebtInstrumentCovenantConsolidatedLeverageRatioMaximum_019cb95f-e9a6-71d5-8e96-0d4c373eece8" xlink:href="msa-20260331.xsd#msa_DebtInstrumentCovenantConsolidatedLeverageRatioMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_DebtInstrumentCovenantConsolidatedLeverageRatioMaximum_019cb95f-e9a6-71d5-8e96-0d4c373eece8" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DebtInstrumentCovenantConsolidatedLeverageRatioInPeriodOfAcquisitionMaximum_019cb95f-e9a6-7758-b374-b9419decb55b" xlink:href="msa-20260331.xsd#msa_DebtInstrumentCovenantConsolidatedLeverageRatioInPeriodOfAcquisitionMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_DebtInstrumentCovenantConsolidatedLeverageRatioInPeriodOfAcquisitionMaximum_019cb95f-e9a6-7758-b374-b9419decb55b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019cb95f-e9a6-70ff-99d5-9bf4aea8042d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019cb95f-e9a6-70ff-99d5-9bf4aea8042d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_RestrictedCashCurrentAssetsIncludedinPrepaidExpensesandOtherCurrentAssets_019cb95f-e9a6-73e2-b186-884540b6343a" xlink:href="msa-20260331.xsd#msa_RestrictedCashCurrentAssetsIncludedinPrepaidExpensesandOtherCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_RestrictedCashCurrentAssetsIncludedinPrepaidExpensesandOtherCurrentAssets_019cb95f-e9a6-73e2-b186-884540b6343a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019cb95f-e9a6-79c1-9ef6-2c9fefd37636" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019cb95f-e9a6-79c1-9ef6-2c9fefd37636" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_LineOfCreditFacilityAmountFinancedIncludingCash_019cb95f-e9a6-7da6-be3a-291d1161bf1c" xlink:href="msa-20260331.xsd#msa_LineOfCreditFacilityAmountFinancedIncludingCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019cb95f-e9a6-7091-9ccd-d4c253ad8665" xlink:to="loc_msa_LineOfCreditFacilityAmountFinancedIncludingCash_019cb95f-e9a6-7da6-be3a-291d1161bf1c" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/GoodwillandIntangibleAssetsNetAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#GoodwillandIntangibleAssetsNetAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/GoodwillandIntangibleAssetsNetAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019cb95f-e9a6-75c3-9182-ad6f305189f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019cb95f-e9a6-761f-856e-30415061e5fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019cb95f-e9a6-75c3-9182-ad6f305189f7" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019cb95f-e9a6-761f-856e-30415061e5fb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a6-74f8-8699-db792fbcc55b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019cb95f-e9a6-761f-856e-30415061e5fb" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a6-74f8-8699-db792fbcc55b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a6-74f8-8699-db792fbcc55b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a6-74f8-8699-db792fbcc55b" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a6-74f8-8699-db792fbcc55b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a6-7889-9c63-b5b8fc343545" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a6-74f8-8699-db792fbcc55b" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a6-7889-9c63-b5b8fc343545" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_019cb95f-e9a6-74f8-805a-3eb32798d236" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a6-7889-9c63-b5b8fc343545" xlink:to="loc_us-gaap_TradeNamesMember_019cb95f-e9a6-74f8-805a-3eb32798d236" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-7cb2-b3c0-7bde6724add4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019cb95f-e9a6-761f-856e-30415061e5fb" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-7cb2-b3c0-7bde6724add4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-7cb2-b3c0-7bde6724add4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-7cb2-b3c0-7bde6724add4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-7cb2-b3c0-7bde6724add4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-74e6-8fb3-52b5ed931744" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a6-7cb2-b3c0-7bde6724add4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-74e6-8fb3-52b5ed931744" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_GlobeHoldingCompanyLLCMember_019cb95f-e9a6-74ed-94a7-05dc05e7c492" xlink:href="msa-20260331.xsd#msa_GlobeHoldingCompanyLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a6-74e6-8fb3-52b5ed931744" xlink:to="loc_msa_GlobeHoldingCompanyLLCMember_019cb95f-e9a6-74ed-94a7-05dc05e7c492" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a6-7bca-8357-1e10281b4b43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_019cb95f-e9a6-761f-856e-30415061e5fb" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a6-7bca-8357-1e10281b4b43" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e9a6-7bca-8357-1e10281b4b43_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a6-7bca-8357-1e10281b4b43" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e9a6-7bca-8357-1e10281b4b43_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e9a6-702f-83d3-5f2f73cf5a4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a6-7bca-8357-1e10281b4b43" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e9a6-702f-83d3-5f2f73cf5a4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AmericasSegmentMember_019cb95f-e9a6-753a-b922-0505f4993305" xlink:href="msa-20260331.xsd#msa_AmericasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e9a6-702f-83d3-5f2f73cf5a4f" xlink:to="loc_msa_AmericasSegmentMember_019cb95f-e9a6-753a-b922-0505f4993305" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_InternationalSegmentMember_019cb95f-e9a6-763b-a6c9-db96e4aebf3e" xlink:href="msa-20260331.xsd#msa_InternationalSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e9a6-702f-83d3-5f2f73cf5a4f" xlink:to="loc_msa_InternationalSegmentMember_019cb95f-e9a6-763b-a6c9-db96e4aebf3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019cb95f-e9a6-7f26-8d20-454c1babfe26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019cb95f-e9a6-75c3-9182-ad6f305189f7" xlink:to="loc_us-gaap_Goodwill_019cb95f-e9a6-7f26-8d20-454c1babfe26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets_019cb95f-e9a6-7bb5-aa77-349781adf14a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_019cb95f-e9a6-75c3-9182-ad6f305189f7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets_019cb95f-e9a6-7bb5-aa77-349781adf14a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/PensionsandOtherPostretirementBenefitsComponentsofNetPeriodicBenefitCostDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#PensionsandOtherPostretirementBenefitsComponentsofNetPeriodicBenefitCostDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/PensionsandOtherPostretirementBenefitsComponentsofNetPeriodicBenefitCostDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019cb95f-e9a7-76d8-8f88-a273fe315f4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019cb95f-e9a7-76d8-8f88-a273fe315f4a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_019cb95f-e9a7-7200-baa0-f3887619a116" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019cb95f-e9a7-76d8-8f88-a273fe315f4a" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_019cb95f-e9a7-7200-baa0-f3887619a116" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019cb95f-e9a7-7200-baa0-f3887619a116_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019cb95f-e9a7-7200-baa0-f3887619a116" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019cb95f-e9a7-7200-baa0-f3887619a116_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_019cb95f-e9a7-7ced-badd-fcf68071d208" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_019cb95f-e9a7-7200-baa0-f3887619a116" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_019cb95f-e9a7-7ced-badd-fcf68071d208" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_019cb95f-e9a7-75eb-ade1-6230c6608198" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019cb95f-e9a7-7ced-badd-fcf68071d208" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_019cb95f-e9a7-75eb-ade1-6230c6608198" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019cb95f-e9a7-7b5e-b7f0-afa3adef19e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_019cb95f-e9a7-7ced-badd-fcf68071d208" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_019cb95f-e9a7-7b5e-b7f0-afa3adef19e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_019cb95f-e9a7-76ae-868a-93bc70936808" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_019cb95f-e9a7-76ae-868a-93bc70936808" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_019cb95f-e9a7-793e-9729-10e63db24414" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_019cb95f-e9a7-793e-9729-10e63db24414" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_019cb95f-e9a7-7004-9ce1-8baeb852e65c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_019cb95f-e9a7-7004-9ce1-8baeb852e65c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_019cb95f-e9a7-7d02-b62c-f3e97f8b5560" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_019cb95f-e9a7-7d02-b62c-f3e97f8b5560" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_019cb95f-e9a7-7776-b517-2a249749b84b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLoss_019cb95f-e9a7-7776-b517-2a249749b84b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019cb95f-e9a7-7389-af16-cd5e6b4f6b45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7f6d-8e04-20f902a32926" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_019cb95f-e9a7-7389-af16-cd5e6b4f6b45" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/PensionsandOtherPostretirementBenefitsAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#PensionsandOtherPostretirementBenefitsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/PensionsandOtherPostretirementBenefitsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7efa-ab23-bafc1474373c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019cb95f-e9a7-7ddf-98bf-413987c1a7e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7efa-ab23-bafc1474373c" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019cb95f-e9a7-7ddf-98bf-413987c1a7e9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019cb95f-e9a7-7195-b963-67cc9ab042e0" 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_ScheduleOfDefinedBenefitPlansDisclosuresTable_019cb95f-e9a7-7ddf-98bf-413987c1a7e9" xlink:to="loc_srt_RangeAxis_019cb95f-e9a7-7195-b963-67cc9ab042e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019cb95f-e9a7-7195-b963-67cc9ab042e0_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_019cb95f-e9a7-7195-b963-67cc9ab042e0" xlink:to="loc_srt_RangeMember_019cb95f-e9a7-7195-b963-67cc9ab042e0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019cb95f-e9a7-7115-8dd9-45ea0f74ba4d" 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_019cb95f-e9a7-7195-b963-67cc9ab042e0" xlink:to="loc_srt_RangeMember_019cb95f-e9a7-7115-8dd9-45ea0f74ba4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019cb95f-e9a7-7f4e-b6aa-daa04e94a8f8" 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_019cb95f-e9a7-7115-8dd9-45ea0f74ba4d" xlink:to="loc_srt_MinimumMember_019cb95f-e9a7-7f4e-b6aa-daa04e94a8f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019cb95f-e9a7-7b56-b9c5-01b36713af86" 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_019cb95f-e9a7-7115-8dd9-45ea0f74ba4d" xlink:to="loc_srt_MaximumMember_019cb95f-e9a7-7b56-b9c5-01b36713af86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_019cb95f-e9a7-7914-8ce5-04188f778c68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7efa-ab23-bafc1474373c" xlink:to="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_019cb95f-e9a7-7914-8ce5-04188f778c68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_019cb95f-e9a7-753f-8e16-23f5ad9e1381" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019cb95f-e9a7-7efa-ab23-bafc1474373c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_019cb95f-e9a7-753f-8e16-23f5ad9e1381" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/AcquisitionsAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#AcquisitionsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/AcquisitionsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7190-9d6e-0c34d0973f2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7190-9d6e-0c34d0973f2e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-73ad-b8b4-4bc199b8705e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7190-9d6e-0c34d0973f2e" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-73ad-b8b4-4bc199b8705e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-73ad-b8b4-4bc199b8705e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-73ad-b8b4-4bc199b8705e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-73ad-b8b4-4bc199b8705e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-723f-809e-9ee1b3f65b6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-73ad-b8b4-4bc199b8705e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-723f-809e-9ee1b3f65b6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MCMember_019cb95f-e9a7-7d91-85d4-78b34fdc4750" xlink:href="msa-20260331.xsd#msa_MCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-723f-809e-9ee1b3f65b6a" xlink:to="loc_msa_MCMember_019cb95f-e9a7-7d91-85d4-78b34fdc4750" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-72d4-a576-7c08b071fd51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7190-9d6e-0c34d0973f2e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-72d4-a576-7c08b071fd51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-72d4-a576-7c08b071fd51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-72d4-a576-7c08b071fd51" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-72d4-a576-7c08b071fd51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-757f-8237-87d1189e05a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-72d4-a576-7c08b071fd51" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-757f-8237-87d1189e05a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_019cb95f-e9a7-797c-b887-52aadbc9258f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-757f-8237-87d1189e05a0" xlink:to="loc_us-gaap_CustomerRelationshipsMember_019cb95f-e9a7-797c-b887-52aadbc9258f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_019cb95f-e9a7-70bd-9ed7-ddf8803b36f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-757f-8237-87d1189e05a0" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_019cb95f-e9a7-70bd-9ed7-ddf8803b36f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_019cb95f-e9a7-74ae-87e4-92cdaa6090e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-757f-8237-87d1189e05a0" xlink:to="loc_us-gaap_TradeNamesMember_019cb95f-e9a7-74ae-87e4-92cdaa6090e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a7-7998-a4f9-eeb20400507c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7190-9d6e-0c34d0973f2e" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a7-7998-a4f9-eeb20400507c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e9a7-7998-a4f9-eeb20400507c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a7-7998-a4f9-eeb20400507c" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e9a7-7998-a4f9-eeb20400507c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019cb95f-e9a7-758f-afcf-b396ae2b5652" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019cb95f-e9a7-7998-a4f9-eeb20400507c" xlink:to="loc_us-gaap_SegmentDomain_019cb95f-e9a7-758f-afcf-b396ae2b5652" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_InternationalSegmentMember_019cb95f-e9a7-71dd-844f-dc8ee5e0e2f4" xlink:href="msa-20260331.xsd#msa_InternationalSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e9a7-758f-afcf-b396ae2b5652" xlink:to="loc_msa_InternationalSegmentMember_019cb95f-e9a7-71dd-844f-dc8ee5e0e2f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AmericasSegmentMember_019cb95f-e9a7-7f8e-ad9e-25df98d748b7" xlink:href="msa-20260331.xsd#msa_AmericasSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019cb95f-e9a7-758f-afcf-b396ae2b5652" xlink:to="loc_msa_AmericasSegmentMember_019cb95f-e9a7-7f8e-ad9e-25df98d748b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019cb95f-e9a7-7ba2-bbec-5130e6d6b1ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019cb95f-e9a7-7ba2-bbec-5130e6d6b1ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019cb95f-e9a7-7f97-aaa6-6c791d684fa7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019cb95f-e9a7-7f97-aaa6-6c791d684fa7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019cb95f-e9a7-7474-9302-fd954ed8bdf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019cb95f-e9a7-7474-9302-fd954ed8bdf4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_019cb95f-e9a7-7f0d-bc43-b55cbf02860e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_019cb95f-e9a7-7f0d-bc43-b55cbf02860e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_FiniteLivedIntangibleAssetExpectedAmortizationYearsOneThroughFour_019cb95f-e9a7-744f-83b6-1c029e39cfd9" xlink:href="msa-20260331.xsd#msa_FiniteLivedIntangibleAssetExpectedAmortizationYearsOneThroughFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_msa_FiniteLivedIntangibleAssetExpectedAmortizationYearsOneThroughFour_019cb95f-e9a7-744f-83b6-1c029e39cfd9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour_019cb95f-e9a7-7b04-8b5d-d6deab8bcbdb" xlink:href="msa-20260331.xsd#msa_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_msa_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour_019cb95f-e9a7-7b04-8b5d-d6deab8bcbdb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019cb95f-e9a7-7cd3-a6e5-ad50c09274a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_Goodwill_019cb95f-e9a7-7cd3-a6e5-ad50c09274a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019cb95f-e9a7-7a5e-baf4-74b8bc839c2c" 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_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019cb95f-e9a7-7a5e-baf4-74b8bc839c2c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019cb95f-e9a7-760d-bbb0-db4330ca6f6c" 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_BusinessAcquisitionLineItems_019cb95f-e9a7-7ff1-9b7f-69516460e2e5" xlink:to="loc_us-gaap_NetIncomeLoss_019cb95f-e9a7-760d-bbb0-db4330ca6f6c" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/AcquisitionsFairValueofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#AcquisitionsFairValueofAssetsAcquiredandLiabilitiesAssumedDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/AcquisitionsFairValueofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7a9c-905c-e72648241fea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7a9c-905c-e72648241fea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-7f97-bb37-51f562db7065" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7a9c-905c-e72648241fea" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-7f97-bb37-51f562db7065" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-7f97-bb37-51f562db7065_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-7f97-bb37-51f562db7065" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-7f97-bb37-51f562db7065_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-7375-8aaa-b64aaedb569a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019cb95f-e9a7-7f97-bb37-51f562db7065" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-7375-8aaa-b64aaedb569a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_019cb95f-e9a7-70c3-ad93-952ef789517d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019cb95f-e9a7-7375-8aaa-b64aaedb569a" xlink:to="loc_us-gaap_CustomerRelationshipsMember_019cb95f-e9a7-70c3-ad93-952ef789517d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-7f9c-94f3-43bf4c0dd40d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019cb95f-e9a7-7a9c-905c-e72648241fea" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-7f9c-94f3-43bf4c0dd40d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-7f9c-94f3-43bf4c0dd40d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-7f9c-94f3-43bf4c0dd40d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-7f9c-94f3-43bf4c0dd40d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-784f-8943-7ef7fbfd9c14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-7f9c-94f3-43bf4c0dd40d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-784f-8943-7ef7fbfd9c14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_MCMember_019cb95f-e9a7-71f8-a3dc-e103b89af4b8" xlink:href="msa-20260331.xsd#msa_MCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-784f-8943-7ef7fbfd9c14" xlink:to="loc_msa_MCMember_019cb95f-e9a7-71f8-a3dc-e103b89af4b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_019cb95f-e9a7-79f0-95c4-fe565fe072f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_019cb95f-e9a7-79f0-95c4-fe565fe072f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019cb95f-e9a7-731c-b6fb-98bdee524446" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_019cb95f-e9a7-79f0-95c4-fe565fe072f3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019cb95f-e9a7-731c-b6fb-98bdee524446" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019cb95f-e9a7-7312-977f-3c69e378f577" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019cb95f-e9a7-7312-977f-3c69e378f577" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_019cb95f-e9a7-76cb-8858-145b9b058c2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_019cb95f-e9a7-76cb-8858-145b9b058c2e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019cb95f-e9a7-7f6e-9920-730cee1ac45f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_Goodwill_019cb95f-e9a7-7f6e-9920-730cee1ac45f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_019cb95f-e9a7-7429-bde7-3c8ae9453095" xlink:href="msa-20260331.xsd#msa_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_msa_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_019cb95f-e9a7-7429-bde7-3c8ae9453095" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_019cb95f-e9a7-75ef-816e-b701a12d48e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_019cb95f-e9a7-75ef-816e-b701a12d48e3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_019cb95f-e9a7-75a0-a0bf-e19f5dc740da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_019cb95f-e9a7-75a0-a0bf-e19f5dc740da" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019cb95f-e9a7-7258-afe4-1b00eb9cf23e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019cb95f-e9a7-7258-afe4-1b00eb9cf23e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019cb95f-e9a7-7a6f-b148-dbf0d3a4663f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019cb95f-e9a7-799d-9c2e-e6d50ca136a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019cb95f-e9a7-7a6f-b148-dbf0d3a4663f" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/DerivativeFinancialInstrumentsAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#DerivativeFinancialInstrumentsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/DerivativeFinancialInstrumentsAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019cb95f-e9a7-7451-9ea0-657a1a6155db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019cb95f-e9a7-7c0e-8f22-0b9b365dbde4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019cb95f-e9a7-7451-9ea0-657a1a6155db" xlink:to="loc_us-gaap_DerivativeTable_019cb95f-e9a7-7c0e-8f22-0b9b365dbde4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019cb95f-e9a7-7f81-8cd0-2662d00c48c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019cb95f-e9a7-7c0e-8f22-0b9b365dbde4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019cb95f-e9a7-7f81-8cd0-2662d00c48c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019cb95f-e9a7-7f81-8cd0-2662d00c48c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019cb95f-e9a7-7f81-8cd0-2662d00c48c5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019cb95f-e9a7-7f81-8cd0-2662d00c48c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019cb95f-e9a7-76b2-a73d-ee65a6ca5a9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019cb95f-e9a7-7f81-8cd0-2662d00c48c5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019cb95f-e9a7-76b2-a73d-ee65a6ca5a9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_019cb95f-e9a7-7878-8867-b09a7fb7f437" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019cb95f-e9a7-76b2-a73d-ee65a6ca5a9b" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_019cb95f-e9a7-7878-8867-b09a7fb7f437" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d86e6-3a76-7e43-a8a4-9dac10fad2d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019cb95f-e9a7-7c0e-8f22-0b9b365dbde4" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d86e6-3a76-7e43-a8a4-9dac10fad2d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019d86e6-3a76-7e43-a8a4-9dac10fad2d8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d86e6-3a76-7e43-a8a4-9dac10fad2d8" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019d86e6-3a76-7e43-a8a4-9dac10fad2d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019d86e6-3a76-75e1-87cf-4de0eaba77ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019d86e6-3a76-7e43-a8a4-9dac10fad2d8" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019d86e6-3a76-75e1-87cf-4de0eaba77ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_019d86e6-3a76-7962-8287-f171c4363204" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019d86e6-3a76-75e1-87cf-4de0eaba77ac" xlink:to="loc_us-gaap_CashFlowHedgingMember_019d86e6-3a76-7962-8287-f171c4363204" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019d86e7-04ea-738f-812f-08e0a51bce6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019d86e6-3a76-75e1-87cf-4de0eaba77ac" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019d86e7-04ea-738f-812f-08e0a51bce6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019d86e6-426f-780c-aff7-d243f2fcf546" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019cb95f-e9a7-7c0e-8f22-0b9b365dbde4" xlink:to="loc_us-gaap_HedgingDesignationAxis_019d86e6-426f-780c-aff7-d243f2fcf546" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019d86e6-426f-780c-aff7-d243f2fcf546_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019d86e6-426f-780c-aff7-d243f2fcf546" xlink:to="loc_us-gaap_HedgingDesignationDomain_019d86e6-426f-780c-aff7-d243f2fcf546_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019d86e6-426f-7bc9-a93c-87cd5bdb192c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019d86e6-426f-780c-aff7-d243f2fcf546" xlink:to="loc_us-gaap_HedgingDesignationDomain_019d86e6-426f-7bc9-a93c-87cd5bdb192c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019d86e6-426f-71a6-ac97-da9919c1c09a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019d86e6-426f-7bc9-a93c-87cd5bdb192c" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019d86e6-426f-71a6-ac97-da9919c1c09a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019cb95f-e9a7-787c-9fb7-eaa9909c01ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019cb95f-e9a7-7451-9ea0-657a1a6155db" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019cb95f-e9a7-787c-9fb7-eaa9909c01ca" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/DerivativeFinancialInstrumentsBalanceSheetLocationandFairValueofAssetsAssociatedwithDerivativeFinancialInstrumentsDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#DerivativeFinancialInstrumentsBalanceSheetLocationandFairValueofAssetsAssociatedwithDerivativeFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/DerivativeFinancialInstrumentsBalanceSheetLocationandFairValueofAssetsAssociatedwithDerivativeFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019cb95f-e9a7-7ac6-b019-5ae5092ebf98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019cb95f-e9a7-793b-817a-4acb8f41eac0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019cb95f-e9a7-7ac6-b019-5ae5092ebf98" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019cb95f-e9a7-793b-817a-4acb8f41eac0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7c22-8ebd-f8145b1ea4cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019cb95f-e9a7-793b-817a-4acb8f41eac0" xlink:to="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7c22-8ebd-f8145b1ea4cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-7c22-8ebd-f8145b1ea4cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7c22-8ebd-f8145b1ea4cd" xlink:to="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-7c22-8ebd-f8145b1ea4cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-77e1-b259-c67f757d2040" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7c22-8ebd-f8145b1ea4cd" xlink:to="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-77e1-b259-c67f757d2040" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019cb95f-e9a7-7849-92b0-10aa310a43b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-77e1-b259-c67f757d2040" xlink:to="loc_us-gaap_NondesignatedMember_019cb95f-e9a7-7849-92b0-10aa310a43b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019cb95f-e9a7-78f2-935a-300e8bf728b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019cb95f-e9a7-793b-817a-4acb8f41eac0" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019cb95f-e9a7-78f2-935a-300e8bf728b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019cb95f-e9a7-78f2-935a-300e8bf728b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019cb95f-e9a7-78f2-935a-300e8bf728b4" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019cb95f-e9a7-78f2-935a-300e8bf728b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019cb95f-e9a7-7875-b7d5-043d32369242" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019cb95f-e9a7-78f2-935a-300e8bf728b4" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019cb95f-e9a7-7875-b7d5-043d32369242" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCurrentLiabilitiesMember_019cb95f-e9a7-7126-be25-647c99e43d9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019cb95f-e9a7-7875-b7d5-043d32369242" xlink:to="loc_us-gaap_OtherCurrentLiabilitiesMember_019cb95f-e9a7-7126-be25-647c99e43d9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_019cb95f-e9a7-794f-8d90-74304e1b2472" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019cb95f-e9a7-7875-b7d5-043d32369242" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_019cb95f-e9a7-794f-8d90-74304e1b2472" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019d6d90-5a02-7a2a-8139-66c03974e6fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019cb95f-e9a7-793b-817a-4acb8f41eac0" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019d6d90-5a02-7a2a-8139-66c03974e6fd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019d6d90-5a02-7a2a-8139-66c03974e6fd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019d6d90-5a02-7a2a-8139-66c03974e6fd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019d6d90-5a02-7a2a-8139-66c03974e6fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019d6d90-5a02-7084-ba40-13fc7725ebe2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019d6d90-5a02-7a2a-8139-66c03974e6fd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019d6d90-5a02-7084-ba40-13fc7725ebe2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019d6d90-5a02-7bd2-b923-e51018ef6d93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019d6d90-5a02-7084-ba40-13fc7725ebe2" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019d6d90-5a02-7bd2-b923-e51018ef6d93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_019cb95f-e9a7-7d50-877b-5a3d3c0c5afa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019cb95f-e9a7-7ac6-b019-5ae5092ebf98" xlink:to="loc_us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_019cb95f-e9a7-7d50-877b-5a3d3c0c5afa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_019cb95f-e9a7-71ae-a859-1c5177adb4bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019cb95f-e9a7-7ac6-b019-5ae5092ebf98" xlink:to="loc_us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_019cb95f-e9a7-71ae-a859-1c5177adb4bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeAssetAtFairValue_019d6d90-5a02-7d5a-8324-b0a9edd70c25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyCashFlowHedgeAssetAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019cb95f-e9a7-7ac6-b019-5ae5092ebf98" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeAssetAtFairValue_019d6d90-5a02-7d5a-8324-b0a9edd70c25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_019d6d90-9218-777a-9655-21feff2bfc87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019cb95f-e9a7-7ac6-b019-5ae5092ebf98" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_019d6d90-9218-777a-9655-21feff2bfc87" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/DerivativeFinancialInstrumentsIncomeStatementLocationandImpactofDerivativeFinancialInstrumentsDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#DerivativeFinancialInstrumentsIncomeStatementLocationandImpactofDerivativeFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/DerivativeFinancialInstrumentsIncomeStatementLocationandImpactofDerivativeFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019cb95f-e9a7-7ebd-9704-004c5c69e5f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019cb95f-e9a7-71f4-94cc-67fe56aa7522" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019cb95f-e9a7-7ebd-9704-004c5c69e5f1" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019cb95f-e9a7-71f4-94cc-67fe56aa7522" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7266-8182-116356113723" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019cb95f-e9a7-71f4-94cc-67fe56aa7522" xlink:to="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7266-8182-116356113723" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-7266-8182-116356113723_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7266-8182-116356113723" xlink:to="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-7266-8182-116356113723_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-73a5-b97e-63b4be9f4726" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019cb95f-e9a7-7266-8182-116356113723" xlink:to="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-73a5-b97e-63b4be9f4726" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019cb95f-e9a7-7454-949b-2eafbd7b68f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019cb95f-e9a7-73a5-b97e-63b4be9f4726" xlink:to="loc_us-gaap_NondesignatedMember_019cb95f-e9a7-7454-949b-2eafbd7b68f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019cb95f-e9a7-7261-ae1f-55d05e98f407" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019cb95f-e9a7-7ebd-9704-004c5c69e5f1" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019cb95f-e9a7-7261-ae1f-55d05e98f407" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/FairValueMeasurementsDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#FairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019cb95f-e9a7-74a3-a033-ad7a2b5fefcd" 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_019cb95f-e9a7-7623-8b6a-25c08dd05748" 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_019cb95f-e9a7-74a3-a033-ad7a2b5fefcd" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019cb95f-e9a7-7623-8b6a-25c08dd05748" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019cb95f-e9a7-730d-8448-04e64f488583" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019cb95f-e9a7-7623-8b6a-25c08dd05748" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019cb95f-e9a7-730d-8448-04e64f488583" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019cb95f-e9a7-730d-8448-04e64f488583_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019cb95f-e9a7-730d-8448-04e64f488583" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019cb95f-e9a7-730d-8448-04e64f488583_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019cb95f-e9a7-7296-bf3b-63669ba084b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019cb95f-e9a7-730d-8448-04e64f488583" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019cb95f-e9a7-7296-bf3b-63669ba084b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019cb95f-e9a7-77eb-9283-59093abbe980" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019cb95f-e9a7-7296-bf3b-63669ba084b4" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019cb95f-e9a7-77eb-9283-59093abbe980" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019cb95f-e9a7-7ef1-b316-7ea4fc038698" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019cb95f-e9a7-77eb-9283-59093abbe980" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019cb95f-e9a7-7ef1-b316-7ea4fc038698" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019cb95f-e9a7-7c85-955d-e0f06d697222" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019cb95f-e9a7-77eb-9283-59093abbe980" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019cb95f-e9a7-7c85-955d-e0f06d697222" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019cb95f-e9a7-7582-9572-121485c79b56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019cb95f-e9a7-74a3-a033-ad7a2b5fefcd" xlink:to="loc_us-gaap_LongTermDebtFairValue_019cb95f-e9a7-7582-9572-121485c79b56" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/CommitmentsandContingenciesAdditionalInformationDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#CommitmentsandContingenciesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/CommitmentsandContingenciesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019cb95f-e9a7-79f4-8ce6-e112692dad87" 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_019cb95f-e9a7-7a35-824d-d815d5d1561e" 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_019cb95f-e9a7-79f4-8ce6-e112692dad87" xlink:to="loc_us-gaap_LossContingenciesTable_019cb95f-e9a7-7a35-824d-d815d5d1561e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019cb95f-e9a7-710b-952c-3c59df8a5fe6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019cb95f-e9a7-7a35-824d-d815d5d1561e" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019cb95f-e9a7-710b-952c-3c59df8a5fe6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_019cb95f-e9a7-710b-952c-3c59df8a5fe6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019cb95f-e9a7-710b-952c-3c59df8a5fe6" xlink:to="loc_us-gaap_LossContingencyNatureDomain_019cb95f-e9a7-710b-952c-3c59df8a5fe6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_019cb95f-e9a7-7b8a-998c-15a18718567d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019cb95f-e9a7-710b-952c-3c59df8a5fe6" xlink:to="loc_us-gaap_LossContingencyNatureDomain_019cb95f-e9a7-7b8a-998c-15a18718567d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_DamagesFromProductSubstancesMember_019cb95f-e9a7-72de-9caa-a9c85ed38eac" xlink:href="msa-20260331.xsd#msa_DamagesFromProductSubstancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_019cb95f-e9a7-7b8a-998c-15a18718567d" xlink:to="loc_msa_DamagesFromProductSubstancesMember_019cb95f-e9a7-72de-9caa-a9c85ed38eac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019cb95f-e9a7-7ea2-8346-7704214c975f" 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_LossContingenciesTable_019cb95f-e9a7-7a35-824d-d815d5d1561e" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019cb95f-e9a7-7ea2-8346-7704214c975f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-7ea2-8346-7704214c975f_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_019cb95f-e9a7-7ea2-8346-7704214c975f" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-7ea2-8346-7704214c975f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-780d-9c47-9f981884d359" 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_019cb95f-e9a7-7ea2-8346-7704214c975f" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-780d-9c47-9f981884d359" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019cb95f-e9a7-7b33-864d-af02d61d2028" 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_019cb95f-e9a7-780d-9c47-9f981884d359" xlink:to="loc_us-gaap_SubsequentEventMember_019cb95f-e9a7-7b33-864d-af02d61d2028" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_LossContingencyPendingLawsuitsNumber_019cb95f-e9a7-774c-bbfd-e71049b38e41" xlink:href="msa-20260331.xsd#msa_LossContingencyPendingLawsuitsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019cb95f-e9a7-79f4-8ce6-e112692dad87" xlink:to="loc_msa_LossContingencyPendingLawsuitsNumber_019cb95f-e9a7-774c-bbfd-e71049b38e41" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_019cb95f-e9a7-7d1d-9d58-f07b22df0827" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019cb95f-e9a7-79f4-8ce6-e112692dad87" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_019cb95f-e9a7-7d1d-9d58-f07b22df0827" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyExpense_019cb95f-e9a7-7fc9-aca3-b06adb9a9b42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductWarrantyExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019cb95f-e9a7-79f4-8ce6-e112692dad87" xlink:to="loc_us-gaap_ProductWarrantyExpense_019cb95f-e9a7-7fc9-aca3-b06adb9a9b42" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.msasafety.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="msa-20260331.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.msasafety.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019cb95f-e9a7-7e7e-9325-accf4944d300" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019cb95f-e9a7-758a-9aab-5352e6f45323" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019cb95f-e9a7-7e7e-9325-accf4944d300" xlink:to="loc_us-gaap_SubsequentEventTable_019cb95f-e9a7-758a-9aab-5352e6f45323" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019cb95f-e9a7-7f9d-853c-d3330cd4b645" 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_SubsequentEventTable_019cb95f-e9a7-758a-9aab-5352e6f45323" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019cb95f-e9a7-7f9d-853c-d3330cd4b645" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-7f9d-853c-d3330cd4b645_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_019cb95f-e9a7-7f9d-853c-d3330cd4b645" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-7f9d-853c-d3330cd4b645_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-7dd0-ad94-aa05abddadf6" 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_019cb95f-e9a7-7f9d-853c-d3330cd4b645" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019cb95f-e9a7-7dd0-ad94-aa05abddadf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019cb95f-e9a7-7e4b-9dc0-5c355d858f8c" 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_019cb95f-e9a7-7dd0-ad94-aa05abddadf6" xlink:to="loc_us-gaap_SubsequentEventMember_019cb95f-e9a7-7e4b-9dc0-5c355d858f8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-703a-a7f3-fc2371c4fea6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019cb95f-e9a7-758a-9aab-5352e6f45323" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-703a-a7f3-fc2371c4fea6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-703a-a7f3-fc2371c4fea6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-703a-a7f3-fc2371c4fea6" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-703a-a7f3-fc2371c4fea6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-7225-8baf-907f78685129" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019cb95f-e9a7-703a-a7f3-fc2371c4fea6" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-7225-8baf-907f78685129" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AutronicaMember_019df45a-528d-79c5-b559-73c694c12bbe" xlink:href="msa-20260331.xsd#msa_AutronicaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019cb95f-e9a7-7225-8baf-907f78685129" xlink:to="loc_msa_AutronicaMember_019df45a-528d-79c5-b559-73c694c12bbe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019df86b-8ad2-781f-b777-1dbd31cf338b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019cb95f-e9a7-758a-9aab-5352e6f45323" xlink:to="loc_dei_LegalEntityAxis_019df86b-8ad2-781f-b777-1dbd31cf338b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019df86b-8ad2-781f-b777-1dbd31cf338b_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019df86b-8ad2-781f-b777-1dbd31cf338b" xlink:to="loc_dei_EntityDomain_019df86b-8ad2-781f-b777-1dbd31cf338b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019df86b-8ad2-78a1-bf78-440546a8619e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019df86b-8ad2-781f-b777-1dbd31cf338b" xlink:to="loc_dei_EntityDomain_019df86b-8ad2-78a1-bf78-440546a8619e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_msa_AutronicaMember_019df86b-a8b8-717b-ab6f-6c050bcb820d" xlink:href="msa-20260331.xsd#msa_AutronicaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019df86b-8ad2-78a1-bf78-440546a8619e" xlink:to="loc_msa_AutronicaMember_019df86b-a8b8-717b-ab6f-6c050bcb820d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019cb95f-e9a7-785e-a9c0-e2284179f230" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019cb95f-e9a7-7e7e-9325-accf4944d300" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019cb95f-e9a7-785e-a9c0-e2284179f230" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityNumberOfEmployees_019df86a-bd9c-7b3b-8a66-83fd575204c1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityNumberOfEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019cb95f-e9a7-7e7e-9325-accf4944d300" xlink:to="loc_dei_EntityNumberOfEmployees_019df86a-bd9c-7b3b-8a66-83fd575204c1" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
