Pronunciation: (out'rī"dur),[key] —n. 1. a mounted attendant riding before or beside a carriage.
2. (at a racetrack) a mounted rider who accompanies or leads a racehorse to the post.
3. a person who goes in advance of an automobile or person to clear a passage.
4. a person who leads the way or is a member of a vanguard; forerunner.
5. a person who rides out or forth, esp. a scout, cowhand, ranch hand, or the like.