When a person needs to take a crap, but no toilet is readily available. You drop your pants, set your coccyx-area down on the bumper of the nearest car, and crap (mostly) onto the ground.

This maneuver is usually performed by a "SF Mission Hipster", after he/she has consumed several Pabst Blue Ribbon beers. Bonus points if the car is a symbol of gentrification, such as a German compact sedan.
Bro #1: Dude. come check out my sweet new BMW 418!

Bro #2: Brah, it looks like someone pulled a bumper dump on you, and missed a bit.

Bro #1: Dude. Lets go back to the Marina and drown our sorrows at Bar None with some beer-pong! Did you bring the rufees?

Bro #2: Brah, I wouldn't have it any other way. Let's go crush some beercans against our foreheads!
by JBlackfoot September 11, 2014
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