n. turncoat, Judas, quisling, betrayer, renegade, fifth-columnist, US Benedict Arnold, Colloq double-crosser, snake in the grass, double-dealer, two-timer Some traitor in their midst had revealed their plans to the enemy
TRAITOR
Meaning of TRAITOR in English
Oxford thesaurus English vocab. Английский словарь Оксфорд тезаурус. 2012