Definition of "pacemaker" [pacemaker]

• Sports One who sets the pace in a race. Also called pacer, pacesetter. (noun)
• A leader in a field: the fashion house that is the pacemaker. Also called pacesetter. (noun)
• A part of the body, such as the mass of muscle fibers of the sinoatrial node, that sets the pace or rhythm of physiological activity. (noun)
• Any of several usually miniaturized and surgically implanted electronic devices used to stimulate or regulate contractions of the heart muscle. (noun)
• Biochemistry A substance that regulates a series of related reactions. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I think the vice president used the term pacemaker plus."
• "I wonder how the average handicapped person with false limbs or a pacemaker is going to like on that scanner …"
• "We all know that heart monitor or pacemaker is just an illusion and has no basis on quantum mechanics."