verb (used with object), bad-mouthed, bad-mouth·ing.
- Slang. to speak critically and often disloyally of; disparage: Why do you bad-mouth your family so much?
- (tr) slang to speak unfavourably about
“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.