Synonyms and related words :
babbler, betrayer, blab, blabber, blabberer, chatterer, delator, fink, gabber, gossip, informer, jabberer, magpie, narc, peacher, prater, prattler, snitch, snitcher, spy, squealer, stool pigeon, stoolie, talebearer, tattler, tattletale, telltale, whistle-blower