THESAURUS
defector
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