While in 5th on the list - the term originates from the early 90's and should be number 1. It has nothing to do with penises or arms.
Windmilling defined: with regards to thrash metal and extreme
music. This
definition predates the others- listed here.
Windmilling is the act of a long haired
metalhead whipping his/her head around in a 360 degree motion, the hair flies up in the air and around- in the shape of a windmill blade.
Did you see that
chick singer windmilling in the that new metal video the other
day? She windmills just as good if not better than some guys can, and looks
hot as hell- doing it!