a big mouth

a big mouth

  (informal)
if you have a big mouth, you talk too much, especially about things that should be secret Helen's got such a big mouth - the news'll be all over the town by tonight. I knew I shouldn't have mentioned the letter. Oh dear, me and my big mouth!
See also: big, mouth
References in classic literature ?
I see and have seen worse things, and divers things so hideous, that I should neither like to speak of all matters, nor even keep silent about some of them: namely, men who lack everything, except that they have too much of one thing--men who are nothing more than a big eye, or a big mouth, or a big belly, or something else big,--reversed cripples, I call such men.
It needn't be from ear to ear, but it's a fact that a big mouth is often a sign of a certain generosity of mind and feeling.