a person in a motor vehicle or on horseback who goes in front of or beside a vehicle as an escort or guard (车辆的)摩托车警卫;骑马侍从 ■(US)a mounted official who escorts racehorses to the starting post (美)把赛马护送到起跑线上的骑马官员 ■(US)a mounted herdsman who prevents cattle from straying beyond a certain limit (美)骑马牧人