(n. pl.) The class Echinodermata which includes the sea urchins. They have a calcareous, usually more or less spheroidal or disk-shaped, composed of many united plates, and covered with movable spines. See Spatangoid, Clypeastroid.
ECHINOIDEA
Meaning of ECHINOIDEA in English
Webster's English dictionary. Английский словарь Webster. 2012