
Have a big mouth
Trust Implications
Using 'have a big mouth' suggests someone may break your trust by talking carelessly.

I didn't invite Clara since she has a big mouth and would've spilled the surprise.
Confidential Matters
It's often used when discussing matters that should be kept confidential or private.

Don't discuss your salary around him; he's got a big mouth.
Informal Context
Considered informal; the phrase isn't used in professional or formal circumstances.

No one in the office talks to him about personal stuff because he has a big mouth.
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