accessory nerven. Either of the 11th pair of cranial nerves, which convey motor impulses to the pharynx and muscles of the upper thorax, back, and shoulders.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.accessory nerve n (Anatomy) either one of the eleventh pair of cranial nerves, which supply the muscles of the head, shoulders, larynx, and pharynx and the viscera of the abdomen and thorax Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014acces?sory nerve` n. either one of the 11th pair of cranial nerves found only in mammals, composed of motor fibers that function in speech and swallowing. [1835?45] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.