An exterior car modification in which you replace the stock bumpers and side skirts with after market ones. Most of the time its purely aesthetic to make your car "faster". But, if your not a stupid teenager, some body kits are actually aerodynamic and CAN add some speed to your car. The amount is small though.
Guy1: I just got this sick lookin' body kit.
Guy2: Dude, It looks like a rice burner.