"Empowering Advanced Learners of English in Business and Academia - TOEFL / ESL / EFL"
Someone who talks too much or reveals others' private matters.
Context : Social Life
Usage of “big mouth”
He has a big mouth. Don't tell him any of your secrets.
Examples of idiom “big mouth” from Twitter
Ah well I have a big mouth. I was laying low for awhile but some things got the best of me.
big mouths ain't so cute...