sphere of influencen. pl. spheres of influence A territorial area over which political or economic influence is wielded by one nation.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.sphere of influence n (Government, Politics & Diplomacy) a region of the world in which one state is dominant Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014sphere? of in?fluence n. any region in which one nation wields dominant power over another or others. [1880?85] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.