a big mouth
1. A tendency or habit of speaking incessantly and indiscreetly, especially about sensitive or secret information. If I'd known you had such a big mouth, I'd have never shared my secret with you! God you've got a big mouth! Don't you ever stop talking about other people's business?
2. A person who talks in such a manner. I can't stand Terry's new husband, he is such a big mouth!
have a big mouth
To have a tendency or habit of speaking incessantly, indiscreetly, and/or in a noisy, boorish manner. I can't stand Terry's new husband, he has such a big mouth! It's like no one else gets a chance to speak when he's here. If I'd known you had such a big mouth, I'd have never shared my secret with you!