A car that appears stock or unimpressive externally but has significant performance modifications. The opposite of a ricer or show build.
Sleeper describes a vehicle that appears stock or unimpressive externally but has been heavily modified for performance. The visual deception is the entire point: a sleeper looks like a normal car (or a slow car) but performs like a much faster one. The aesthetic is the opposite of show-car culture and the opposite of ricer aesthetics.
Classic sleeper examples include grandma-spec sedans with V8 swaps, station wagons with turbo conversions, minivans with race engines, and economy cars with significant power upgrades hidden under stock sheet metal. The common thread is that someone seeing the car at a stoplight would assume it is slow, only to be surprised when it accelerates dramatically.
Building a successful sleeper requires restraint. Wheels and tires must be appropriate for the car's appearance (factory-style 16-inch wheels look slow even when the car is fast). Exterior modifications must be minimal or invisible. Loud exhaust ruins the effect. Some builders go further and intentionally add elements that make the car look slower (faded paint, rust, missing hubcaps).