INFORMER

n. 25B6; noun INFORMANT, betrayer, traitor, Judas, collaborator, stool pigeon, fifth columnist, spy, double agent, infiltrator, plant; telltale, taleteller; N. Amer. tattletale; informal rat, squealer, whistle-blower, snake in the grass, snitch; Brit. informal grass, supergrass, nark, snout; Scottish informal clype; N. Amer. informal fink, stoolie.