| reaction engine or reaction motor | |
| —n | |
| an engine, such as a jet or rocket engine, that ejects gas at high velocity and develops its thrust from the ensuing reaction | |
| reaction motor or reaction motor | |
| —n | |
| a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison. |
| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |