n. Any of several extinct fishlike jawless vertebrates having a heavily armored body; of the Paleozoic. [ WordNet 1.5 ]
‖prop. n. pl. [ NL., fr. Gr. 'o`strakon shell of a testacean + &unr_; skin. ] (Zool.) A suborder of fishes of which Ostracion is the type. [ 1913 Webster ]