(n.) A tattler; a telltale.

absurdity amphigory babble babblement balderdash bavardage be indiscreet be unguarded betray betray a confidence betrayer bibble-babble blab blabberer blabbermouth blah-blah blather blether blethers blurt blurt out bombast bull bullshit cackle caquet caqueterie chat chatter chatterer chitter-chatter clack claptrap clatter delator dither double-talk drivel drool fiddle-faddle fiddledeedee fink flummery folderol fudge fustian gab gabber gabble galimatias gammon gas gibber gibberish gibble-gabble give away go on gobbledygook gossip guff gush haver hocus-pocus hot air humbug idle talk inform inform on informer jabber jabberer jargon jaw leak let drop let fall let slip magpie mere talk mumbo jumbo narc narrishkeit natter niaiserie nonsense nonsense talk pack of nonsense palaver patter peach peacher piffle pour forth prate prater prating prattle prattler prittle-prattle ramble on rant rat rattle rattle on reel off reveal a secret rigamarole rigmarole rodomontade rubbish run on sing skimble-skamble snitch snitcher spill spill the beans spout spout off spy squeal squealer stool stool pigeon stoolie stuff and nonsense stultiloquence talebearer talk talk away talk nonsense talk on talkee-talkee tattle tattle on tattler tattletale tell on tell secrets tell tales telltale tittle-tattle trash trumpery twaddle twattle twiddle-twaddle vapor vaporing waffle waffling whistle-blower yak yakkety-yak