/ Thesaurus / S Synonyms of synapsid Find synonyms for: Noun1. synapsid, synapsid reptile, reptile, reptilianusage: extinct reptile having a single pair of lateral temporal openings in the skullWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: languid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language