spark gapn. A gap in an otherwise complete electric circuit across which a discharge occurs at a prescribed voltage.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.spark gap n (Electronics) the space between two electrodes across which a spark can jump. Sometimes shortened to: gap Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014spark? gap` n. 1. a space between two electrodes, across which a discharge of electricity may take place. 2. the electrodes and the space between, considered as a unit: used in ignition systems. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.