'keep quiet' definitions:

Definition of 'keep quiet'

(from WordNet)
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]

Synonyms of 'keep quiet'

From: Moby Thesaurus