n. One who, or that which, paces. [ 1913 Webster ]
2.Especially: A horse trained to a special gait in which both feet on one side leave the ground together; a horse that paces. [ wns=2 ] [ WordNet 1.5 ]
3. A horse used to set the pace in racing. [ wns=3 ] Syn. -- pacemaker, pacesetter. [ WordNet 1.5 ]