1. (n.) One who informs, animates, or inspires.

2. (n.) One who informs, or imparts knowledge or news.

3. (n.) One who informs a magistrate of violations of law; one who informs against another for violation of some law or penal statute.

Benedict Arnold Brutus Judas Judas Iscariot Quisling accusant accuser adviser allegator announcer annunciator appellant archtraitor attestant attestator attester authority betrayer blab blabber blabberer blabbermouth bystander canary channel claimant cockatrice cojuror communicant communicator complainant compurgator conniver conspirator conspirer delator deponent double agent double-crosser double-dealer earwitness enlightener expert witness eyewitness fink gossipmonger grapevine grass impeacher impugner indictor informant information center information medium interviewee intrigant intriguer libelant machinator monitor mouthpiece narc nark newsmonger notifier party passerby peacher petitioner plaintiff plotter press prosecutor public relations officer publisher quisling radio rat reporter schemer serpent snake snitch snitcher source spectator spokesman spy squealer stool stool pigeon stoolie suitor swearer talebearer taleteller tattler tattletale television teller telltale testifier the prosecution timeserver tipster tout traitor treasonist trimmer turncoat voucher weasel whistle-blower witness