Entry 1 sense Webster, 1913 Malfeasance /mălˌ-fēz'-əns/ · Mal·fea·sance · IPA /ˌmælˈfiːzəns/ 01 n. The doing of an act which a person ought not to do; evil conduct; an illegal deed. 1. The doing of an act which a person ought not to do; evil conduct; an illegal deed.(Law)