A specific type of motorcycle, typically distinguished by it's aerodynamic 'hunched-over' seating position and high power to weight ratio. Often favoured by stunters, who choose the bikes because they are light and easy to perform tricks (such as wheelies and stoppies) on.
Crotch rockets are not always Japanese motorcycles, Italian companies such as Ducati manufacture quite high-quality crotch rockets as well.
Also known as 'sportbikes'.
The Ducati 999, Suzuki GSXR1000 and Yamaha YZF-R1 are good examples of ~1000cc crotch-rockets.