normal distributionn. A theoretical frequency distribution for a random variable, characterized by a bell-shaped curve symmetrical about its mean. Also called Gaussian distribution.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.normal distribution n (Statistics) statistics a continuous distribution of a random variable with its mean, median, and mode equal, the probability density function of which is given by (exp-[(x??)2/2?2]/??(2?)) where ? is the mean and ?2 the variance. Also called: Gaussian distribution Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014nor?mal distribu?tion n. a theoretical frequency distribution represented by a normal curve. Also called Gaussian distribution. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.