SYNONYMS
informant
collaborator, fifth columnist, double agent, spy, infiltrator, whistle-blower, plant
betrayer, traitor, Judas, double-crosser, turncoat
North American tattletale
informal rat, squealer, stool pigeon, stoolie, telltale, tale teller, snake in the grass, canary, snitch, peacher
British informal grass, supergrass, nark, snout, nose
Scottish informal clype
Scottish, Northern Irish informal tout
North American informal fink
Australian, New Zealand informal fizgig, pimp, shelf
archaic intelligencer, beagle