knucklehead 

From the 1930's (circa). Refers to a person of questionable intelligence. The size of the brain being given relative size of a human knuckle. Similar to pinhead.

That guy just sat on a bench with wet paint. What a knucklehead.

knucklehead by The Phat Doctor December 27, 2004

knucklehead 

A dunce. A dummy. A very stubborn person or animal.

I told him how to do it, but he would not listen, the knucklehead!

knucklehead by Merrily McCarthy July 17, 2003

knucklehead 

a person who doesn't listen, and stays in trouble

Dat boy a knucklehead he stay in trouble.

knucklehead by J-Wilk May 21, 2007

knucklehead 

Engine produced by the Harley Davidson Motorcycle Company from(1936 to 1947). The engine consists of an overhead-valve v-twin design with covers on the valves that resembled knuckles, hence the name of "knucklehead".

Mike's knucklehead got repo'd after he missed his second payment

knucklehead by The B-rad October 14, 2006

Knucklehead 

A nickname associated with fans of the heavy metal band Five Finger Death Punch.

Judging by his 5FDP shirt, he must be a Knucklehead.

Knucklehead by Tank238 October 15, 2012

knucklehead 

someone who is irresponsible and acts ignorant

Don't be a knucklehead you understand what's being said.

knucklehead by Gerard Irick October 21, 2010

knucklehead 

the punching of a boner in attempts to make it go away.

dude I got a boner in the parking lot so I gave myself some knucklehead to make it go away.

knucklehead by knuckleheadwittness February 20, 2012