Wiktionary
n. Any engine that generates thrust by expelling matter, especially hot gases produced by igniting a fuel; either a rocket engine or several types of jet engine.
WordNet
n. a jet or rocket engine based on a form of aerodynamic propulsion in which the vehicle emits a high-speed stream [syn: reaction-propulsion engine]
Wikipedia
A reaction engine is an engine or motor which provides thrust by expelling reaction mass, in accordance with Newton's third law of motion. This law of motion is most commonly paraphrased as: "For every action force there is an equal, but opposite, reaction force".
Examples include both jet engines and rocket engines, and more uncommon variations such as Hall effect thrusters, ion drives, mass drivers and nuclear pulse propulsion.
Usage examples of "reaction engine".
You can't tell a left-handed monkey wrench from a reaction engine, yet you ask me for blue prints of a space ship.
A rope was tied around the handrail, looped over a beam, and held a long heavy rod suspended over the centre of the reaction engine.
Something to do with the Third Law of Emotion, and the mind as a Reaction Engine.
She came barreling across the dunes in a four-wheel Aston Assbuster, model XJ, with a reaction engine and a bilious tangerine-flake paint job.
She saw the reaction engine she had been carrying spin away, its polished surfaces sending out flashes of reflected light.
Air-lock gang are out there right now, sawing the reaction engine off so she'll just about fit through the door.