A description applied to a girl with large breasts, a large butt, but who is otherwise thin and scrawny. The term comes from the fact that she is distributed weight-wise similar to a flywheel, implying that if she started to fall she would roll.
Man, you should've seen this girl: skinny but with a gorgeous rack a huge ass. She was a total flywheel.
by Notmiefault February 19, 2011