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English definition of “big mouth”

big mouth

noun [C usually singular]     informal disapproving
If someone is or has a big mouth , they often say things that are meant to be kept secret : He is/has such a big mouth . He went and opened his big mouth and told them the whole story .People who reveal secrets and tell tales
(Definition of big mouth noun from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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