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2 definitions by Unknown Dropouts

 
1.
When you're running down the stairs very quickly in boxer shorts, and the weight of your testicles causes your scrotum to move against your gooch and make a loud clapping sound.
John: Ew, Mike. Yesterday I was running down the stairs and I did a stairclap. My mom heard. She looked grossed out.
Mike: EWW! DUDE, I DIDN'T NEED TO KNOW YOU HAVE A NASTY STAIRCLAP!
by unknown dropouts March 29, 2011
 
2.
Like a wet willy, but when you shove your dick in someone's belly button.
Mary: I got a wet wilkie, it was terrorising rape.
by Unknown Dropouts May 30, 2011