When sick with the stomach flu, pinwheeling is the unfortunate act of simultaneously projectile vomiting out one end while shooting explosive diarrhea out the other. So named for its resemblance to a pinwheel firework, which emits a strong stream of sparks in opposite directions in order to spin.

It's the sweat that accumilates under big boobs

The act of twirling your boner out the sun roof of a moving vehicle to elicit interest from the opposite sex.

When using a Mac and your cursor become an infinitely spinning pinwheel. Often occurring when a programme crashes or when too many applications are opened/being opened at once.

the act of rapidly spinning your penis while taking a piss.

A unfortunate side effect of being rather ill, and your body evacuates from both exits.