em·o·din (?m??-d?n?)n. An orange crystalline compound, C15H10O5, that is obtained from rhubarb and other plants and has cathartic, anti-inflammatory, and anticancer properties.[New Latin (Rheum) ?m?d?, a species of rhubarb : genitive of ?m?dus (from Greek ?m?dos, the Himalayas) + -in.]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.emodin (??m??d?n) n (Elements & Compounds) chem a chemical compound obtained from, primarily, rhubarb rootCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014