/ Thesaurus / S Synonyms of sea urchin Find synonyms for: Noun1. sea urchin, echinodermusage: shallow-water echinoderms having soft bodies enclosed in thin spiny globular shellsWordNet 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