head flap 

A flap or roll of usually fat filled skin at the back of peoples heads revealed by baldness. Usually grows in prominence with age, weight gain, and the relentless pull of gravity.

Plural: Head Flappage

The term "head flap" came to prominence in the mid-1990's when Philadelphia teens would play a game called "Head Flap Slap Crack Trap". The game involved slapping head flaps while sticking opened packets of mayonnaise down the back of the pants. The person had to say "Head Flap Slap" and "Crack Trap" as they were doing the respective tasks in order for it count. When the prankee went to see what was in their pants they often squished the mayo into their pants which was the primary goal of the prank, the head slap being more of a diversionary tactic. This would leave a noticeable white glob that left the prankee with some embarrassed explaining to do.

"Those fools searched my body everywhere for the money but they forgot to check my head flap!"

"What is that smell?" "Gunther probably forgot to wash behind his head flap again..."

"Despite the bitter chill, the back of Walters' head remained comfortably warm due to his impressive head flappage."

head flap by Ham Pony February 20, 2018

flap head 

derogatory term for Canadians

origin: South Park animation of Canadians

Don Cherry is a flap head.
Why are so many flap heads so funny?
That lousy flap head ganked all my beer after the hockey game.

flap head by John-Michael Davis June 14, 2006

Flappy head

A person addicted to the infamous mobile game "Flappy Bird".

Ole' boy over there is a full on flappy head, straight fiending for some bird through pipe action.

Flappy head by Awol239 February 13, 2014