Fastback
A fastback is an automotive styling feature which is defined by the rear of the car having a single slope from the roof to the rear bumper.Some models (such as the Ford Mustang) have been specifically marketed as a fastback, often to differentiate the model from other body styles (e.g. coupe models) in the same model range.
Hatchback
A hatchback is a car with a hatch-type rear door that opens upwards and often a shared volume for the passenger and cargo areas.
When the body style of a car is described as a hatchback, typically it is referring to a utilitarian small car; however hatchback doors are also used on several sports cars, SUVs and large luxury cars. The modern form of the hatchback body style was developed through the 1960s and rose in popularity through the 1970s.
Fastback (noun)
A motor car having a continuous slope from the roof to the rear
Hatchback (noun)
A car with a sloping, hinged rear door that opens upwards.
Hatchback (noun)
The door itself.