Any kind of deteriorated vehicle, usually the kind that mom and dad make you drive in high school. Popular shitwagons include the Chevette, Pinto, Yugo, Festiva, etc.
"You got a car, dude?"
"Yeah, but it's a real shitwagon."
another term for a station wagon, mini-van, or any other kind of vehicle that is targeted at the "family" demographic(also M.A.V.)
"Tactical advantages aside, the M.A.V. is top of the line for the holy warrior troop transport manufactured by the Church of Latter Day Saints Military Industrial Complex. Also great for family trips...to heathen lands."