tv. to speak ill of someone or something. (See also dirty mouth; poor-mouth.) : I wish you would stop bad-mouthing my car.
n. someone who speaks ill of someone or something. : Harry is such a bad-mouth!
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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Disparage or criticize unduly, malign, as in Why do you constantly bad mouth your colleagues? This term is believed to be of African origin, where the phrase bad mouth signifies a curse or evil spell. [1930s]
