The term "flat lemon" essentially refers to a citrus fruit that lacks the traditional rounded shape and instead appears flattened or squashed. While there may not be an official synonym for this specific term, there are certainly other phrases that could be used to describe a similar fruit shape. For instance, the word "oblate" means flattened or depressed, which could be used to describe a lemon that has lost its typical roundness. Alternatively, some people might refer to a flattened lemon as a "pancake lemon" or a "disc lemon," both of which capture the essence of its unique appearance.