out·rid·er / ˈoutˌrīdər/ • n. a person in a motor vehicle or on horseback who goes in front of or beside a vehicle as an escort or guard: an escort of police outriders. ∎ a person or thing that accompanies or precedes another, esp. as a precursor: gray-white cumulus clouds—outriders of the storm. ∎ a mounted official who escorts racehorses to the starting post. ∎ a cowhand who prevents cattle from straying beyond a certain limit.DERIVATIVES: out·rid·ing / ˌoutˈrīding/ n.