"Wast foul-mouthed" is a vulgar and offensive way to describe someone who uses profanity excessively. To express this trait in a more refined and mature manner, there are several synonyms that can be used, such as 'vulgar', 'obscene', 'crass', 'offensive', 'abusive', 'profane', 'blasphemous', 'indecent', 'vulgar', 'coarse', 'vile', or 'lewd'. These words depict the use of improper language or behavior that can cause discomfort and offense to others. By choosing a more tactful and appropriate synonym, we can convey the same meaning without resorting to crude language or derogatory statements.