kneeslapper 

When one finds something extremely amusing, while seated the person slaps their own knee in jubilation.

That joke was a hellava kneeslapper, I laughed my ass off.

kneeslapper by Count Funkula June 13, 2003

Kneeslapper 

The most extravagant reaction to something of funny, or toast-worthy nature, where someone uses their hand to make contact with their knee typically in a very absurd and flamboyant manner.

Guy: hey guess what
Guy#2: what?
Guy: UR MOM
Guy: performs a kneeslapper

Kneeslapper by Toastingurmom May 8, 2018

kneeslapper 

Someone with a dick so big it slaps there knees while walking.

When ol boy pulled his kneeslapper out; she knew she was going to be walking with a limp the next day..

kneeslapper by lilsmarterthanaboxofrocks March 25, 2021

Kneeslapper 

A joke that's supposed to be funny but isn't really. And all you want to do is make the person not feel bad, but the joke isn't funny. So..... you just say "that's a real kneeslapper!"

Jim: Knock Knock.
You: Who's there?
Jim: Tree!

You: Tree who?
Jim: Tree Fifty!
You: THATS A KNEESLAPPER

Kneeslapper by TheAwokenMyth April 11, 2017

kneeslapper 

something you use when a jokes not funny but you want to make the person feel better about themselves.

friend 1:why did the chicken cross the road
friend 2:idk why...
friend 1:to get to the other side
friend 2's mind:unfunniest shit ive ever heard god damn learn some humor
friend 2:wowee what a kneeslapper!oh geez you really got me with that one!!!

kneeslapper by angelkitty June 19, 2023

That's a kneeslapper 

A phrase coined by a particular person who does theatre is lebanese and is super smart

THAT'S A KNEESLAPPER FOR SURE FOR SURE
*slaps knees wildly with a crazed look in her eyes*

That's a kneeslapper by avamarie-is-super-pretty October 11, 2022

Polish kneeslapper 

An acknowledgment of a bad joke by slapping your knee in an obviously sarcastic manner. Antonym: kneeslapper. Synonym: dad joke.

HA! That's a good Polish kneeslapper, Chad! HA! Ha!! ha!!!

Polish kneeslapper by Champ Liberty August 3, 2019