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