Synonyms and related words :
Benedict Arnold, Brutus, CIA man, Judas, Judas Iscariot, Quisling, archtraitor, betrayer, cloak-and-dagger operative, cockatrice, conniver, conspirator, conspirer, counterintelligence agent, counterspy, double-crosser, double-dealer, espionage agent, informer, inside man, intelligence agent, intrigant, intriguer, machinator, military-intelligence man, naval-intelligence man, operative, plotter, quisling, rat, reconnoiterer, schemer, scout, secret agent, serpent, snake, spotter, spy, spy-catcher, timeserver, traitor, treasonist, trimmer, turncoat, undercover man