pacer

noun6

1. •
   One who paces.
2. •
   In harness racing, a horse with a gait in which the front and back legs on one side take a step together alternating with the legs on the other side; as opposed to a trotter.
3. •
   A horse whose natural gait is a pace (where the legs of the same side are lifted together).

   • And the hill-king spake to his footpages twain. Time with me goes slow. — "Put ye the gray pacers now unto the wain," But that grief is heavy I know. — 1828
4. •
   A pacemaker (one who sets the pace in a race).
5. •
   A timer in an electric toothbrush that indicates how long the user should spend brushing in each part of the mouth.
6. •
   (Australia) A mechanical pencil.

noun1

1. •
   A British lightweight railbus diesel multiple unit of class 140, 141, 142, 143 or 144.