apos·ta·tize \əˈpästəˌtīz also -ȯs-\intransitive verb (-ed/-ing/-s) Etymology: Middle French or Late Latin; Middle French apostatiser, from Late Latin apostatizare, from Latin apostata + -izare -ize : to commit apostasy : to renounce one's faith, party, or principles < the church had apostatized and gone against the commandment — Edson Jessop >