| Noun | 1. | pacemaker - a leading instance in its field; "the new policy will be a pacesetter in community relations"exemplar, good example, example, model - something to be imitated; "an exemplar of success"; "a model of clarity"; "he is the very model of a modern major general" | |
| 2. | pacemaker - a specialized bit of heart tissue that controls the heartbeat | |
| 3. | pacemaker - an implanted electronic device that takes over the function of the natural cardiac pacemaker | |
| 4. | pacemaker - a horse used to set the pace in racing | |