heart·beat (härt?b?t?)n.1. a. A single complete pulsation of the heart.b. The general nature of the heart’s contractions or the rate at which they occur: the baby’s heartbeat; a fast heartbeat.2. A vital force or driving impulse: Broadway is the heartbeat of the New York City theater world.3. An instant: I’ll be there in a heartbeat.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.heartbeat (?h??t?bi?t) n (Physiology) one complete pulsation of the heart. See diastole, systoleCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014heart?beat (?h?rt?bit) n. a pulsation of the heart, including one complete systole and diastole. Idioms: in a heartbeat, Informal. enthusiastically and without hesitation; in an instant. [1840?50] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.