The antonyms for the phrasal verb "ate out" could include words like cooked in, dined in, prepared at home, or even packed lunch. Eating out typically refers to dining at a restaurant or ordering takeout, whereas the aforementioned antonyms would imply cooking and eating at home. Other antonyms could further include terms like fasted, starved, or abstained, which would indicate a deliberate decision not to eat out or prepare food at home. Choosing the appropriate antonym for the context would depend on the speaker's intention and the degree of contrast they want to make with "ate out".