The windmill is a pretty good looking dunk/layup, its when u swing the ball in a circular motion in the air, thus looking like the blades of a windmill. KZ did a double windmill meaning he swung the ball twice (720) in the air then dunked it.

Here's marbury windmilling it...
http://www.youtube.com/watch?v=JYi3uo4KsxE

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