open (one's) mouth

(redirected from opens their mouth)

open (one's) mouth

To say something, especially that which is indiscreet, boorish, or meant to be a secret. Why did you have to open your mouth about my crush on Tommy? Why couldn't you just keep it between us? You've got to make sure that he never opens his mouth about what went on here today.
See also: mouth, open
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

open your (big) ˈmouth

(informal) say something when you should not: Why do you always have to open your big mouth? Can’t you just keep quiet sometimes?
See also: mouth, open
Farlex Partner Idioms Dictionary © Farlex 2017
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References in periodicals archive ?
ck oo mwwt "What kind of 'man' opens their mouth and talks about something when they have your number but they don't talk to you?
The mouth insert lights up when the wearer opens their mouth, providing a glowing smile, reports the Daily Mail.
It is bearable when Richard Burton adds a bit of class to proceedings, but burn-your-stereo-annoying when anyone opens their mouth to sing.