A person or animal who is asleep.
A person with a specified sleep pattern: "he was a light sleeper".
A term often referring to what appears to be a ordinary looking stock vehicle that is anything but stock under the hood.
A sleeper (US English) or Q-car (British English) is a car that has high performance and an unassuming exterior. Sleeper cars are termed such because their exterior looks little or no different from a standard or economy-class car. In some cases the car appears worse due to seeming neglect on the owner's part, typically referred to as "all go and no show". While appearing to be a standard or neglected car, internally they are modified to perform at much higher performance levels.
We're particularly a big fan of sleepers, it seems the 400whp barrier has been broken, with a new beast is now hitting the streets.