It's hard to say what a coupe is anymore. Is it merely a car with two doors? Does it have to have an arching roofline? Do frameless windows count for anything? Can a five-door hatchback or even an SUV be a coupe? At some point in the last few years, nearly everything we thought made a coupe a coupe has been challenged by something that calls itself a coupe, but to most people isn't. Our friends at BMW have led most of this line of questioning.