Pacemaker - Definition

n 1: a leading instance in its field; "the new policy will be a
pacesetter in community relations" [syn: pacesetter,
pacemaker]
2: a specialized bit of heart tissue that controls the heartbeat
[syn: pacemaker, cardiac pacemaker, sinoatrial node,
SA node]
3: an implanted electronic device that takes over the function
of the natural cardiac pacemaker [syn: pacemaker,
artificial pacemaker]
4: a horse used to set the pace in racing [syn: pacer,
pacemaker, pacesetter]