'shut one's mouth' definitions:

verb

Refrain from divulging sensitive information; keep quiet about confidential information; "Don't tell him any secrets --he cannot keep his mouth shut!" [syn: keep quiet, shut one's mouth, keep one's mouth shut] [ant: babble, babble out, blab, blab out, let the cat out of the bag, peach, sing, spill the beans, talk, tattle]