tris·kai·dek·a·pho·bi·a (tr?s?k?-d?k??-f??b?-?, tr?s?k?-)n. An abnormal fear of the number 13.[Greek treiskaideka, thirteen (treis, three; see trei- in Indo-European roots + kai, and + deka, ten; see deca-) + -phobia.]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.triskaidekaphobia (?tr?ska??d?k??f??b??) n (Psychology) an abnormal fear of the number thirteen[C20: from Greek triskaideka thirteen + -phobia] ?triskai?deka?phobic adj, nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014tris?kai?dek?a?pho?bi?a (?tr?s ka??d?k ??fo? bi ?, ?tr?s k?-) n. fear or a phobia concerning the number 13. [1910?15;