sea urchin /ˈsi ˌɝtʃɪ̈n/ noun1 •Any of many marine echinoderms, of the class Echinoidea, commonly found in shallow water, having a complex chewing structure named Aristotle's lantern.Of the many species of sea urchins utilized in biological research today the most widely used in North America is probably the purple sea urchin, Strongylocentrotus purpuratus. — 1986 formssea urchins
