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1.
n. A suspicious automobile, often a police car. The word "sketch-wagon" is most often used by people participating in illegal activities, such as speeding or running a red light, and is mostly associated with smoking marijuana.

(Can also referred to as "Sketch-Mobile.")
Michael ran a red light and thought he'd gotten away with it, when a sketch-wagon appeared out of nowhere and pulled him over.
by ihasabike December 15, 2010