An expression used to say "got you" in
jest, sometimes to
razz a friend/provoke a reaction. You might even suggest something deragotary about them that you know is not true, just to see their reaction/get them excited. Then you usually then say "waah"! to them to let them know you were just trying to
screw around and get them going.
Eric is
a joker and wants to get his pal Bill, who is obsessed with hygiene, going. They have both just stepped out of their dorm showers and Bill has just finished putting on his deodorant etc.:
Eric: "Geez Bill, you still smell extra rank today - didn't you just take a shower too?"
Bill (with a very
puzzled look on his face): "Yeah, i guess. Maybe i should see a doctor"
Eric (with a big smile on his face): "
WAAH"!