Simple past tense and past participle of badmouth.(verb)
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Use "badmouthed" in a sentence
"I know she is getting badmouthed, which is really unfortunate, but she is a good person."
"There's deposition testimony from Cuban in which he acknowledges that he withheld consulting fees from Nelson in 2006 because he believed the former coach had "badmouthed" the team during the NBA finals and should be made to "beg" for the money."
"There's testimony from Cuban in which he acknowledges withholding consulting fees from Nelson because he believed the former coach had "badmouthed" the team during the NBA finals and should be made to "beg" for the money."