Bad-mouthing refers to speaking negatively about someone or something in a derogatory manner. There are many synonyms for bad-mouthing that can be used interchangeably, such as slandering, disparaging, maligning, defaming, vilifying, and smearing. These words all share the common theme of spreading negative information or misconceptions about someone or something with the intent of harming their reputation. Other synonyms for bad-mouthing may include derogatory, critical, negative, or damaging language. When used in the appropriate context, using synonyms for bad-mouthing can help make your writing or speech more colorful and expressive, while conveying the same meaning.