average deviation n (Statistics) statistics another name for mean deviation Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014mean? devia?tion n. Statistics. a measure of dispersion, computed by taking the arithmetic mean of the absolute values of the deviations of the functional values from some central value, usu. the mean or median. Also called average deviation. [1890?95] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.