What is the real definition for a "supercar"? Is it super fast? or super luxurious? What super things does a car need to do to become a supercar?

Recently I have seen this term thrown around a bit to much. Yahoo is running an article right now about a new BMW supercar; the i8. And while the i8 has the potential to be an interesting and exciting sport coupe, I would not go as far as to call it a supercar.

The show "How its Made" recently ran a series special on high end cars, where they covered Ferrari, Porsche, Maserati, and other exotic type manufacturers. The one show where they used the term "supercar" was when they were covering the rolls Royce Phantom. Sure, it is super luxurious, and it does perform well for its size, but supercar???

To me, a supercar is something that was built to break limits (not just the bank)... The Jaguar XJ220, for example, was once the holder of the worlds fastest production vehicle. It did this with a V6 engine; that's pretty super to me. On the other hand, the 458 Italia, which achieves massive amounts of down force without the use of a traditional wing type spoiler, is still just a high end sports car. Impressive, but nothing overly super about it.

Where do we draw the line?