Synonyms and related words :
apostate, backslider, bolter, collaborationist, collaborator, convert, deserter, fifth columnist, mugwump, proselyte, quisling, rat, recidivist, recreant, renegade, renegado, renegate, reversionist, runagate, schismatic, seceder, secessionist, separatist, strikebreaker, tergiversant, tergiversator, traitor, turnabout, turncoat, turntail