Weak sauce is a slang term used to describe something that is weak, unimpressive, or lacks substance. However, there are a variety of synonyms you can use instead of weak sauce such as feeble, insipid, bland, lackluster, limp, meager, pathetic, unsatisfactory, inadequate, and powerless. All these synonyms might describe something that fails to make an impact or simply falls short of expectations. For example, you can use feeble to describe an argument that lacks any strong points or insipid to refer to a flavor that lacks any real taste. These synonyms can help you elevate your language and better articulate your thoughts.