keep mouth shut

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keep (one's) mouth shut

To not discuss or mention something. He needs to keep his mouth shut and stop telling our family secrets to everyone in town!
See also: keep, mouth, shut

keep one's mouth shut (about someone or something)

Fig. to keep quiet about someone or something; to keep a secret about someone or something. They told me to keep my mouth shut about the boss or I'd be in big trouble. I think I'll keep my mouth shut.
See also: keep, mouth, shut