Definitions for jet engine
Random House Webster's College Dictionary
an engine, as of an aircraft, that produces forward motion by the rearward exhaust of a jet of fluid or heated air and gases.
a gas turbine produces a stream of hot gas that propels a jet plane by reaction propulsion
an engine that obtains thrust by taking in air at the front, using it to burn fuel, then ejecting the hot combustion products at the rear through a propulsive nozzle
any engine propelled by expelling a high speed fluid jet (jet propulsion), such as a rocket, turbojet, turbofan, ramjet etc.