di·met·ro·don (d?-m?t?r?-d?n?)n. Any of various carnivorous pelycosaurs of the genus Dimetrodon of the Permian Period, having long spines on the back that supported a sail-like structure, and powerful jaws with sharp teeth.[New Latin Dimetrod?n, genus name : Greek di-, two; see di-1 + Greek metron, measure; see m?- in Indo-European roots + Greek od?n, tooth (from its having two different kinds of teeth); see dent- 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.di?met?ro?don (da??m? tr??d?n) n. an extinct carnivorous mammallike reptile of the North American Permian genus Dimetrodon, with high spines along the back. [