Out-smart is a term used to describe defeating someone in a battle of wits or intelligence. The antonyms for out-smart can be divided into several categories. One is "out-dumb," which implies making a mistake or failing to understand something. Other options include "out-muscle," "out-power," or "outmatch," which indicate a superior level of physical or mental strength. Another option might be "out-flank," meaning to approach a problem from a different angle or to take an indirect route to success. Ultimately, the choice of antonym will depend on the context and the desired meaning of the sentence.