Opened their mouths - Idioms by The Free Dictionary
open (one's) mouth (redirected from opened their mouths)
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.
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?
References in periodicals archive
To impale prey with these impressive weapons, the famous sabretoothed cats must have opened their mouths
wider than any modern big cat, but it was unclear if their jaw muscles were strong enough to do it.
NOW that Jack Straw and Tony Blair have opened their mouths
about veils it seems everyone wants to have a go at us Muslims.
They spread their arms and opened their mouths
in a silent cry.