dys·to·ni·a (d?s-t??n?-?)n. Abnormal tonicity of muscle, characterized by prolonged, repetitive muscle contractions that may cause twisting or jerking movements of the body or a body part.dys·ton?ic (-t?n??k) adj.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.dystonia (d?s?t??n??) n (Pathology) a neurological disorder, caused by disease of the basal ganglia, in which the muscles of the trunk, shoulders, and neck go into spasm, so that the head and limbs are held in unnatural positions[from dys- + -tonia from Greek tonos tension, from teinen to stretch]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014dys?to?ni?a (d?s?to? ni ?) n. a neurological disorder marked by strong involuntary muscle spasms that cause painful and disabling twisting of the body. [1955?60] dys?ton?ic (-?t?n ?k) adj. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.