mouth off

mouth off idiom
  1. Complain or express one's opinions loudly and indiscreetly, as in She was always mouthing off about the other members. [Slang; 1960s]
  2. Speak impudently, talk back, as in He got in trouble by mouthing off to his teacher. [Slang; 1960s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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