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bad-mouth

or bad·mouth

[bad-mouth or, sometimes, -mouth]
See more synonyms for bad-mouth on Thesaurus.com
verb (used with object), bad-mouthed, bad-mouth·ing.
  1. Slang. to speak critically and often disloyally of; disparage: Why do you bad-mouth your family so much?

Origin of bad-mouth

1935–40; originally a curse, spell (the sense recorded in Gullah); compare Vai (Mande language of Liberia and Sierra Leone) dà nyà mà curse, literally, bad mouth
Related formsbad-mouth·er, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for bad-mouth

belittle, criticize, disparage, knock, malign, pan, rap, rip, roast, slam, slander, dis
British Dictionary definitions for bad-mouth

bad-mouth

verb
  1. (tr) slang to speak unfavourably about
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for bad-mouth
v.

"abuse someone verbally," 1941, probably ultimately from noun phrase bad mouth (1835), in Black English, "a curse, spell," translating an idiom found in African and West Indian languages. Related: Bad-mouthed; bad-mouthing.

Online Etymology Dictionary, © 2010 Douglas Harper