A fastback is an automotive styling feature, defined by the rear of the car having a single slope from the roof to the tail.
The kammback is not a fastback design with a roofline that tapers downward toward the car's rear before being cut off abruptly.
Some models, such as the Ford Mustang, have been marketed explicitly as fastbacks, often to differentiate them from other body styles (e.g. coupé models) in the same model range.