phrase made popular by rapper Noreaga or NORE. it can be used as a greeting like what up. or in a fight when you win, then get up in that bitches face and be like, what what!
If you can't remember WHAT it was you were doing last weekend or WHAT the guys name is that owns Berkshire Hathaway LLC, or WHAT that persons name was you were just talking to, then you would confer with an associate on a "what what" ie. you need help cause you need a "what what."