TATTLETALE
tattletale, tattler, taleteller, talebearer, telltale, blabbermouth
(noun) someone who gossips indiscreetly
Source: WordNet® 3.1
Etymology
Adjective
tattletale (not comparable)
telltale; giveaway
Noun
tattletale (plural tattletales)
One who tattles (reports others' wrongdoings), often a child seeking attention.
Synonyms: tattler, whistle-blower, narc, snitch, Thesaurus:informant
One who gossips, often for the sake of attention.
Synonyms: gossip, rumourmonger, Thesaurus:gossiper
Verb
tattletale (third-person singular simple present tattletales, present participle tattletaling, simple past and past participle tattletaled)
(ambitransitive) To act as a tattletale; to tell on; to give away, reveal, or expose.
Source: Wiktionary