when one does not wear the proper under garment underneath the shirt... or none at all
i.e. to describe free wheeling on/off on/off red light, green light, caution
where a woman rides in a car with her tits exposed. there are several ways she can do this. She can stand up through a moon roof, ride in a convertible, in the back of a pickup truck ect.
Derives from tits being called wheels.
look at that woman free wheeling.