motor-mouth

[ moh-ter-mouth ]
/ ˈmoʊ tərˌmaʊθ /

noun, plural mo·tor-mouths [moh-ter-mouths, mouth z] /ˈmoʊ tərˌmaʊθs, ˌmaʊðz/. Slang.

a person who is a constant or irrepressible talker.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019