A group of nine friends who make weird jokes and react to them by saying "that's a knee slapper, har de har har" and slapping their knees.
Knee slapper #1"And then the whale said, wait whales can't talk!" the Knee slappers "That's a knee slapper, har de har har!"
by A knee slapper April 07, 2013
adverb. A term used to describe a dumb-ass joke. Its inception was the result of someone noticing their friend slapping their thigh/knee when a joke was told. It's an official "knee slapper" when the person laughing sqints their eyes, slaps their knee, and can barely speak due the amount of laughimg taking place. This definition is considered a "knee slapper".
by MegDar September 21, 2009
by SALKFJsalfk February 18, 2008
by Erak22 September 28, 2009
by JarMa13 December 04, 2018
Guy 1: what do you call cheese that isn't yours?
Guy 2: Idk what?
Guy 1: nacho cheese
Guy 2: now that's a knee-slapper!!!
Guy 2: Idk what?
Guy 1: nacho cheese
Guy 2: now that's a knee-slapper!!!
by billystiggle December 10, 2011
something really funny (from the slapping of the knees and hitting the floor associated with laughter.
by The Return of Light Joker August 03, 2008