action potentialn. A momentary change in electrical potential on the surface of a cell, especially of a nerve or muscle cell, that occurs when it is stimulated, resulting in the transmission of an electrical impulse.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.action potential n (Physiology) a localized change in electrical potential, from about ?70 mV to +30 mV and back again, that occurs across a nerve fibre during transmission of a nerve impulse Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ac?tion poten`tial n. the change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals. Compare nerve impulse. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.action potential – A brief electrical signal transmitted along a nerve or muscle fiber following stimulation.See also related terms for nerve.Farlex Trivia Dictionary. © 2012 Farlex, Inc. All rights reserved.