If you are looking for synonyms for the term "be foul-mouthed", then you have come to the right place. The phrase refers to someone who is using crude and offensive language, often to insult or upset others. The synonyms include "cursing", "swearing", "using profanity", "uttering obscenities", "vulgar language", "off-color remarks", "scatological language", and "invective". These words are used to describe someone who has a tendency to use language that is not acceptable in polite society. Being foul-mouthed is not generally considered a desirable trait, and it can lead to people feeling uncomfortable or offended.