A turbine engine, in which the rotating turbine stages output power to a shaft. Due to the high rotational speed of a turboshaft engine, they are usually coupled to reduction gears to match them to whatever apparatus they power. Turboshaft engines can be found on helicopters, some boats, trucks, and Jay Leno's motorcycle. Turboshaft engines are much more efficient than conventional piston engines in most applications, and will run on nearly any fuel. They also last a lot longer, especially if run continuously at high speed, since a conventional engine's reciprocating mechanism tends to pound itself to death. The only reason I can see that you probably don't have one in your car is that they have a turbo lag from hell.