i already ate

used to reject someone trying to make plans. similar to "I have a boyfriend" but has more uses.

Person A: "Hey, wanna get Taco Bell?"
Person B: "No thanks, I already ate."

I already 'ate it yesterday

When one bitches about a certain topic, another my reply with this phrase to indicate that they already had a distaste for the subject matter. The joke can be extended to "I have already eaten it."

I hate maths homework.
Mate, I already 'ate it yesterday.