The phrase "not ate" refers to the absence of eating. Therefore, the antonyms for "not ate" would be words that describe eating or consuming food. For instance, one such antonym would be "ate," which indicates the action of consuming food. Other antonyms for "not ate" could be "feasted," "gobbled," "devoured," "consumed," "ingested," "dined," "noshed," "indulged," "chewed," "swallowed," "munched," and "gorged." All of these words describe the act of eating and therefore can be used as antonyms for "not ate.