Stairclap 

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!

Stairclap by unknown dropouts April 15, 2011

Staircase 

A ramp with teeth

Don't worry, the staircase won't bite!

Staircase by America Lover 🇺🇸 November 18, 2019

staircase wit

thinking of the right answer too late; the perfect, usually piercing, riposte that you conceive only when replaying a verbal exchange later in your head

from the French l'esprit d'escalier, the witty repartee you thought of as you're going downstairs to leave

My coworker Ann had taken to calling me "Markus", which I hate. I told her I hated it, and her response was,"It's a term of affection."

I muttered something like "Well it's not".

What I SHOULD have said:
Considering her name, "OK, to cement this 'affectionate' relationship, I'll call you An(n)us."

staircase wit by Mandingoe July 14, 2004

Shit staircase

When a group of people shits in the toilet, but decides not to flush, thus creating a shit staircase to the rim of the toilet

Cleaner1 "Those students are filthy bastards"
Cleaner2 "Why?"
Cleaner1 "They left a shit staircase in the lavatory"
Cleaner2 "Filthy Students"

Shit staircase by dirtydom February 20, 2010

staircase warrior 

a person who fulfills their sexual urges in a staircase.

1st Guy- “Bro that girl a staircase warrior don’t fuck with her”
2nd Guy- “ Fucking in a staircase is crazy… you right i won’t fuck w ha”

staircase warrior by Nolafiona87 December 3, 2022

step down the staircase 

when your ex dated someone new who’s a significant step down from you.

“hey chloe, show me your ex’s new gf”
“omg ok”
*shows photo*
“wow she is definitely a step down the staircase”

step down the staircase by mill234567 June 14, 2019

Stair Clap 

The clapping of a male's scrotum against his inner thigh when he runs down or maybe even up stairs.

When Tommy ran down stairs excitedly, he Stair Clapped and got sick from the impact.

Stair Clap by schaeferqwaefer November 22, 2009