From Longman Dictionary of Contemporary Englishbig mouthbig mouthspokenTELL A SECRET someone who has a big mouth cannot be trusted to keep things secret I’m sorry. I shouldn’t have opened my big mouth.me and my big mouth (=said when you wish you had not told someone a secret) → bigmouth → big
Examples from the Corpus
big mouth• If Britain is a body then Essex is the botty and Barnsley's the great big mouth.• To her sisters, she is simply a big mouth.• Director Jafar Panahi clearly loves children for what they are, big mouths and all.• The final proof, or perhaps the first, is the chub's big mouth and thick white rubbery lips.• But I kept my big mouth shut.• I generally think of sushi as bite-sized, but at Sushi-Cho you need a big mouth to eat your sushi without embarrassment.• And to have a big mouth to project.big mouthbig mouthinformalTALK TO somebody if someone has a big mouth, they say too much or tell another person’s secrets → mouthExamples from the Corpus
big mouth• And to have a big mouth to project.• I generally think of sushi as bite-sized, but at Sushi-Cho you need a big mouth to eat your sushi without embarrassment.• To her sisters, she is simply a big mouth.• Director Jafar Panahi clearly loves children for what they are, big mouths and all.• If Britain is a body then Essex is the botty and Barnsley's the great big mouth.• But I kept my big mouth shut.• The final proof, or perhaps the first, is the chub's big mouth and thick white rubbery lips. 