If you are looking for synonyms for the term "is foul-mouthed," then there are several options available to you, depending on the context. Some possible alternatives include "uses profanity," "speaks rudely," "swears uncontrollably," "has a potty mouth," "utters foul language," and "is vulgar in speech." Each of these phrases can convey a similar sense of someone who speaks in a manner that is offensive or inappropriate, often using obscene or offensive language. Whether you are describing a coworker, friend, or family member, these synonyms can help you find the right words to convey your message effectively.