Blabbermouth

Part of speech: noun

Pronunciation: /ˈblæb.ə(ɹ)ˌmaʊθ/

Definitions

1. A person who talks excessively and cannot keep secrets or confidential information private
2. a person who discloses secrets or speaks incessantly without regard for discretion
3. someone incapable of restraint in conversation who reveals private matters carelessly

Etymology: "Blabbermouth" is a plain compound: "blabber" joined to "mouth," with the sense of someone whose mouth runs on without restraint. "Blabber" is the older and more basic word here, and it is the element that carries the idea of chattering or babbling. Its origin is imitative, reflecting the sound of loose, rapid talk, and it has been used for indiscreet talkers for a long time. Adding "mouth" turns the act into a person, so the noun names the one who cannot keep a secret. The result is a word that describes its subject in the most literal way available. Rather than naming a habit, it points to the body part doing the work, a pattern common in English nicknames for indiscreet people. The compound is transparent enough that speakers rarely need to think about either part.

Synonyms: talker, chatterbox, gossip, jabberer, windbag

Antonyms: quiet, reserved, taciturn, silent, reticent