arrhythmica disturbance in rhythm, as in the heartbeatNot to be confused with:eurhythmic ? characterized by a pleasing rhythm; harmoniously proportionedAbused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreear·rhyth·mic (?-r?th?m?k)adj. Lacking rhythm or regularity of rhythm: “a slight arrhythmic imperfection when the car idles” (Garrison Keillor).ar·rhyth?mi·cal·ly adv.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.arrhythmic , arhythmic or arythmicadjhaving irregular rhythmCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014