The antonyms for the phrase "knowing stuff" can refer to a lack of knowledge or awareness. Some possible antonyms could include phrases like "ignorant of," "uninformed about," and "unfamiliar with." On the other hand, synonyms for "knowing stuff" might include phrases like "well-informed," "knowledgeable," and "educated." These words convey the idea that the person in question has a deep and extensive understanding of a particular subject matter or area of interest. Whether you're looking to describe someone's level of expertise, or simply trying to convey the opposite of "knowing stuff," there are many different ways to communicate your message effectively.