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1. verb To speak negatively or unflatteringly about someone or something. Why are you always bad-mouthing Tiffany? You don't even know her that well!
2. noun One who says negative or unflattering things about someone or something. He's a real bad-mouth, so don't listen to anything he says about me!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

bad-mouth someone or something

to say negative things about someone or something. Mr. Smith was always bad-mouthing Mrs. Smith. They just didn't get along. John bad-mouths his car constantly because it is too small for him.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

bad mouth

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]
See also: bad, mouth
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.


1. tv. to speak ill of someone or something. (see also dirty mouth, poor-mouth.) I wish you would stop bad-mouthing my car.
2. n. someone who speaks ill of someone or something. Harry is such a bad-mouth!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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References in periodicals archive ?
But he also took the chance to bad-mouth his X Factor nemesis on stage.
All you can do is love him, be there when he needs it, but don't bad-mouth her to him.
Be kind to your dad, and don't let them bad-mouth each other in front of you.
The first thing any person associated with Royalty should be made aware of is never, and I mean never, bad-mouth anyone.
It hadn't been going too well recently but Joe's humour didn't fail and I never heard him complain or bad-mouth anyone.
So next time you're tempted to bad-mouth big Duncan when he mauls a would-be entrepreneur in the Dragons' Den, pause for a moment and think of all the good work he does away from the glare of the studio.
Don't bad-mouth her - tell her that addiction is an illness and stress how much her mum loved her and how proud she will be to see her grow up and not repeat her mum's fate.
Meaning utter misery for the car-owning majority, as the streets fill up with non road tax-paying Lycra warriors who stop drivers turning left, bad-mouth them and bang their wing mirrors at traffic lights for entering their "lane" by a few centimetres as they wobble through the rush hour in pursuit of a smaller bottom.
Randal is happy to bad-mouth everything and everyone that moves, but Dante is about to get married and head off for a better life in Florida.
We agreed to be civilised about access and not to fight in front of the kids or bad-mouth each other.
ACTS threatened with legal action if they "bad-mouth" the show.
I try very hard not to bad-mouth their dad in front of them, even though I think it.
To a question, he said that PTI, Chief Imran Khan wasted one and half year of the nation and he bad-mouthed every institution standing on the container.
Barton had bad-mouthed the town of Burnley during a Twitter row last year while Johnson announced on transfer deadline day that he was delighted to be joining a team called 'Derby City'.
There are comforting things they can say to her that she cannot accept from you, especially if you've bad-mouthed him.