big mouth

noun, plural big·mouths [big-mouth z, -mouths] /ˈbɪgˌmaʊðz, -ˌmaʊθs/ for 1; (especially collectively) big·mouth, (especially referring to two or more kinds or species) big·mouths for 2.

1. a loud, talkative person, especially one who lacks discretion.
2. any of several fishes having an unusually large mouth.

noun

1. slang a noisy, indiscreet, or boastful person