The expression "won't wash" usually refers to something that is not believable or convincing. Its antonyms could be phrases such as "holds water," "rings true," or "stands up to scrutiny." These phrases suggest that the argument or explanation is well-supported and credible. Additionally, antonyms for "won't wash" include the terms "plausible" and "convincing," indicating that the idea presented is reasonable and convincing. In contrast, synonyms for "won't wash" include phrases such as "doesn't add up," "doesn't make sense," and "isn't plausible." All in all, antonyms for "won't wash" imply that the argument or explanation is trustworthy and believable.
