Pronunciation: (rā'sur),[key] —n. 1. a person, animal, or thing that races or takes part in a race, as a racehorse, bicycle, yacht, etc.
2. anything having great speed.
3. See racing skate. 4. a turntable on which a heavy gun is turned.
5. any of several slender, active snakes of the genera Coluber and Masticophis.