1.) When you finger a chick and then give her a wet willy with the finger that was previously in her vagina.
2.) When you skip to world nine via the whistles obtained from Level 1-3 and the World 1 Minifortress.
3.) But mostly it's the first defintion.
Guy A: "Oh shit, son. I whistle tricked that bitch so bad that she couldn't hear for a week."
Guy B: "Heh, heh, heh."
Guy A: "Yeh, yeh son, dawg."
Guy A: "Hey you playing Mario 3? Did you try the whistle trick I told you about?"
Guy B: "Yeah... she punched me in the balls."