reaction engine

WordReference Random House Unabridged Dictionary of American English © 2025

reac′tion en′gine, [Aeron., Rocketry.]

1. Aeronautics, Rocketry, Rocketry an engine that produces power as a reaction to the momentum given to gases ejected from it, as a rocket or jet engine. Also called reac′tion mo′tor. 

• 1865–70

Collins Concise English Dictionary © HarperCollins Publishers::

reaction engine, reaction motor noun

1. an engine, such as a jet or rocket engine, that ejects gas at high velocity and develops its thrust from the ensuing reaction