Pacemaker

[peys-mey-ker] /ˈpeɪsˌmeɪ kər/

noun
1.
.
2.
Medicine/Medical. an electronic device implanted beneath the skin for providing a normal heartbeat by electrical stimulation of the heart muscle, used in certain heart conditions.
3.
Anatomy, Physiology. any specialized tissue that governs a rhythmic or cyclic biological activity, as the sinoatrial node of the heart that controls heartbeat.
/ˈpeɪsˌmeɪkə/
noun
1.
a person, horse, vehicle, etc, used in a race or speed trial to set the pace
2.
a person, an organization, etc, regarded as being the leader in a particular field of activity
3.
Also called cardiac pacemaker. a small area of specialized tissue within the wall of the right atrium of the heart whose spontaneous electrical activity initiates and controls the beat of the heart
4.
Also called artificial pacemaker. an electronic device for use in certain cases of heart disease to assume the functions of the natural cardiac pacemaker
n.

also pace-maker, 1884, originally a rider or boat that sets the pace for others in training. Meaning “the node of the heart whivh determines the beat rate” is from 1910; sense of “man-made device for stimulating and regulating heartbeat” is from 1951. From pace (n.) + maker.

pacemaker pace·mak·er (pās’mā’kər)
n.

pace’mak’ing adj. & n.
pacemaker
(pās’mā’kər)

A group of specialized muscle fibers in the heart that send out impulses to regulate the heartbeat. If the heart’s built-in pacemaker does not function properly, an artificial pacemaker may be necessary — a small electrical device that also regulates the heartbeat by sending out impulses. An artificial pacemaker may be placed inside the body surgically or may be worn outside.