• (n. pl.) An order of Entomostraca possessing hard bivalve shells. They are of small size, and swim freely about.
Os`tra·coi'de·a noun plural [ New Latin , from Greek ... shell of a testacean + -oid .] (Zoology) An order of Entomostraca possessing hard bivalve shells. They are of small size, and swim freely about. [ Written also Ostracoda .]