car·di·a (kär?d?-?)n. pl. car·di·ae (-d?-??) or car·di·as 1. The opening of the esophagus into the stomach.2. The upper portion of the stomach that adjoins this opening.[Greek kardi?, heart, cardiac orifice of the stomach; see kerd- in Indo-European roots.]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.cardia (?k??d??) na lower oesophageal sphincterCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014car?di?a (?k?r di ?) n., pl. -di?ae (-di?i) -di?as. an opening that connects the esophagus and the upper part of the stomach. [1775?85;