The phrase "shapes up" typically refers to the idea of improving or becoming better. Some antonyms for this phrase include deteriorate, decline, worsen, regress, and deteriorate. When something "shapes up," it suggests progress and positive change, while its antonyms suggest the opposite. For example, if an athlete's performance in a sport is "shaping up," it means they are improving and performing better. Conversely, if their performance "deteriorates," it means they are declining and getting worse. Therefore, antonyms for "shapes up" are often used to describe negative situations where improvements are not being made, or things are getting worse.