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When any members of a particular driver's family, friends, or school mates (including girlfriends and boyfriends) take a moist poop in the passenger seat of said driver's car.
Heather made shotgun-soup in Dave's car, causing them to break up when even bleach would not remove the smell.

See: poop shotgun burger king drive-by
by Frank N. Stien January 28, 2011
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