The term "foul-mouthed" usually refers to someone who speaks in an inappropriate, vulgar manner. Antonyms for this term could include "polite," "well-mannered," "respectful," "courteous," and "thoughtful." These terms describe individuals who are considerate of others and use language that is appropriate for the situation. People who are "foul-mouthed" may be seen as offensive and disrespectful, while those who use polite language may be seen as more likable and trustworthy. In many cases, being polite and respectful in conversation can lead to more positive personal and professional relationships, while using foul language can lead to negative perceptions and consequences.