indefeasible Syllabification: (in·de·fea·si·ble)Pronunciation: /ˌindəˈfēzəbəl/Definition of indefeasible adjective chiefly Law & Philosophy not able to be lost, annulled, or overturned:an indefeasible rightDerivatives indefeasibilityPronunciation: /-ˌfēzəˈbilitē/ noun indefeasiblyPronunciation: /-blē/ adverb indefeasible in other Oxford dictionaries Definition of indefeasible in the British & World English dictionary