To speak negatively or critically about someone or something; to insult or disparage.
From 'bad' + 'mouth.' This is a phrasal compound that developed in American English, possibly with influences from African American Vernacular English, becoming standard in the mid-20th century.
Badmouthing someone online has consequences you can't undo—screenshots are forever, and what you said in anger can follow someone for years because the internet never forgets!
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