Originally Posted by wikipedia

Supercar is a term used most often to describe an expensive high end car. It has been defined specifically as "a very expensive, fast or powerful car". Stated in more general terms: "it must be very fast, with sporting handling to match," "it should be sleek and eye-catching" and its price should be "one in a rarefied atmosphere of its own
However, the proper application of the term is subjective and disputed, especially among enthusiasts. So-called vehicles are typically out of the ordinary and are marketed by automakers to be perceived by the public as unusual. The supercar can take many forms including limited production specials from an "elite" automaker, standard looking cars made by mainstream companies that hide massive power and performance, as well as models that appeal to "hardcore enthusiasts" from "manufacturers on the fringe of the car industry."