An expensive, exotic, ridiculously fast, and generally impractical sports car, the kind that rock stars drive. Italian makes like Ferrari, Maserati, and Lamborghini are excellent examples of rockstarmobiles, but a convertible V8 Ford Mustang with all the features and options can also serve this purpose.
"As soon as he got a big record deal with Sony, he went out and bought this rockstarmobile Lamborghini. Hope the record is a hit or he's gonna be in deep shit."