Synonyms and related words :
Trojan horse, apostate, backslider, bolter, collaborationist, collaborator, convert, crypto, defector, deserter, fellow traveler, fifth column, fraternizer, mugwump, proselyte, quisling, recidivist, recreant, renegade, renegado, renegate, reversionist, runagate, saboteur, schismatic, seceder, secessionist, security risk, separatist, strikebreaker, subversive, tergiversant, tergiversator, traitor, turnabout, turncoat, turntail, underground