I'd say that a AAA game is a PS3 game that some sony's fans think its going to push PS3 sales to the top, making it the best selling console of this generation within a month after release.... :P joke
Well, I don't like that term either, because now any title can be a AAA.
I think a AAA should:
-Sell extremely well
-Average above 90
-Be from a serie loved by fans, or create a new one
1 2 3 not only you and me.
Livin' in sin is the new thing.