A small four-cylinder vehicle (i.e. Honda Civic) usually painted yellow, pink, or purple and driven by a 5'5" jackass. The wagon usually has a large wing on the back, white rims, and an annoying loud muffler.
Chuckfelt like he was like Fast and The Furious as he rolled through Philly in his douche wagon.
Very similar to a butt wagon, though a bit more oriented toward people who deserve a heavier term than butt wagon. A douche wagon can also safely be called a buttsnoipe, an asshaberdasher, a bunghole, etc.