by Unknown Dropouts October 27, 2011
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!
Mike: EWW! DUDE, I DIDN'T NEED TO KNOW YOU HAVE A NASTY STAIRCLAP!
by unknown dropouts April 15, 2011