from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of various echinoderms of the class Echinoidea, having a soft body enclosed in a round, symmetrical, calcareous shell covered with long spines.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any of many marine echinoderms, of the class Echinoidea, commonly found in shallow water, having a complex chewing structure named Aristotle's lantern
from the GNU version of the Collaborative International Dictionary of English
- Any one of numerous species of echinoderms of the order Echinoidea.
from The Century Dictionary and Cyclopedia
- n. An echinoid; any member of the Echinoidea; a sea-egg or seahedgehog.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. shallow-water echinoderms having soft bodies enclosed in thin spiny globular shells
sea + urchin (meaning hedgehog), due to the similarity in appearance to the hedgehog. (Wiktionary)