The phrase "be top heap" means to be at the top of a group or to be the best. Some antonyms of this phrase include "be bottom tier," which means to be at the bottom of a group, or "be mediocre," which means to be average or ordinary. Another antonym is "be subpar," which means to be below the expected or desired level. Additionally, "be inferior" is an antonym of "be top heap," meaning to be of lower quality or lower in rank. Lastly, "be lackluster" is another antonym, which means to be unimpressive or dull. Overall, these antonyms encompass the opposite of being at the top of a group or being the best.