Keep your mouth shut
Also found in: Acronyms.
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! A: "It wasn't my fault. Brian said&mdash" B: "Keep your mouth shut, Chad!"
Keep your mouth shut (about someone or something).
Fig. Do not tell anyone about someone or something. Bob: Are you going to see the doctor? Mary: Yes, but keep your mouth shut about it. Bob: Isn't Tom's uncle in tax trouble? Jane: Yes, but keep your mouth shut about him.