"Black-mouthed" is an adjective that describes someone who speaks or behaves in a rude or offensive manner. However, there are many synonyms for this word, each highlighting a specific aspect of such behavior. "Vulgar-tongued" refers to someone who uses profanity or crude language. "Ill-mannered" suggests someone who lacks proper etiquette and social grace. "Disrespectful" characterizes behavior that shows a lack of regard for other people's feelings or beliefs. "Brusque" means someone who is abrupt or curt in speech. "Crass" indicates someone who lacks refinement or sensitivity. "Rude" captures behavior that is impolite or discourteous. "Impolite," "insensitive," and "uncivil" are additional synonyms to describe this type of behavior.