hex·a·dec·i·mal (h?k?s?-d?s??-m?l)adj.1. Of, relating to, or based on the number 16: the hexadecimal number system.2. Of or relating to sixteenths.n.1. A number system having 16 as its base.2. A sixteenth.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.hexadecimal (?h?ks??d?s?m?l) adj (Computer Science) relating to or using a number system whose base is 16 rather than 10n (Computer Science) a number system having a base 16; the symbols for the numbers 0?9 are the same as those used in the decimal system, and the numbers 10?15 are usually represented by the letters A?F. The system is used as a convenient way of representing the internal binary code of a computerCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014hex?a?dec?i?mal (?h?k s??d?s ? m?l) adj. 1. of or pertaining to a numbering system that uses 16 as the radix and that represents digits greater than 9 with the letters A through F. 2. relating to or encoded in such a system, esp. for use by computers. [1955?60] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.