Clement of Alexandria, Saint ad 150?-220? Greek Christian theologian whose writings incorporate elements of Gnosticism and Platonism.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.Clement of Alexandria n (Biography) Saint. original name Titus Flavius Clemens. ?150??215 ad, Greek Christian theologian: head of the catechetical school at Alexandria; teacher of Origen. Feast day: Dec 5 Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Clem?ent of Alexan?dria n. (Titus Flavius Clemens) A.D. c150?c215, Greek Christian theologian and writer. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.