thing-in-it·self (th?ng??n-?t-s?lf?)n. pl. things-in-them·selves (th?ngz??n-th?m-s?lvz?) Philosophy See noumenon.[Translation of German Ding an sich.]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.thing-in-itself n (Philosophy) (in the philosophy of Kant) an element of the noumenal rather than the phenomenal world, of which the senses give no knowledge but whose bare existence can be inferred from the nature of experience Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014thing?-in-itself? n., pl. things?-in-themselves?. (in Kantian philosophy) reality as it is apart from experience. Compare noumenon. [1650?60; translation of German Ding an sich] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.