When someone's listening to hard rock/heavy metal reaches to an epic level, normal headbanging can't coupe with the sheer power of it. That's when windmilling comes to play.
Goes great if the person has long hair and a brain as strong an Air Force pilot's ('cause it'll gives you some fucking powerful headaches if you're not careful).
Windmill headbanging, harder to do but much more fun to watch than normal headbanging.
"Fuck, man! Listening to Amon Amarth, Morbid Angel and Cannibal Corpse is giving me the urge to windmill my head off!"
When you propel your man meat in a circular motion mimicking that of a helicopter or a windmill. When inertia has reached its apex one may exert their cosmic dong clock onto un-expecting objects and/or bystanders. Perfected by Willy Nelson in the late 1980's, this of courseinspiring his hit single "whip that sausage right round."
Slappee: Why does my head hurt?
Slapper: Well my good sir, due to the omega Windmill Dick Slap I had bestowed onto your forehead, you had slipped into a coma for 27 years 36 days only to be awoken by yet another Windmill Dick Slap to your forehead. And that my friend is why your head hurts.