An interjection used to put extreme emphasis on a recently said joke, insult, or otherwise entertaining comment; an interjection used in great delight to one other's comment.
Jack: Bob, what's two plus two?
Jerk: You know what's so great about the internet? There's something called a "search engine" and you can find the answer to any question on it.
Bob: I'm not sure that the search engine works. I searched for "dumbass responses," and you're line didn't show up!
Jack and Bob: AIOO!!!!!!