A stunna is a person, usually a male, defined by, but not limited to, the following characteristics:
Driving a car, often a Honda or other slow import, "hunched over," with the left hand at the top of the wheel and half the upper body well past the right edge of the seat.
Driving in the above described position with a visor hanging from the windshield.
Adorning the exterior of one's vehicle with useless body kits, vinyl graphics, company logos, wings, etc.
and neons in the interior of the car, and having a stereo system loud enough to shake a 2 block radius while being heavy enough to sink the vehicle to the bumpstops.
Wearing a hat, preferrably of "trucker" style, sideways and/or only half on the head.
see trucker hat
see von dutch
Numerous more exist, but the main have been outlined above.