an·os·tra·ca \əˈnästrəkə\noun plural Usage: capitalized Etymology: New Latin, from an- + -ostraca : an order of small aquatic crustaceans (subclass Branchiopoda) lacking a carapace, having stalked eyes and 11 to 19 pairs of thoracic appendages, and including Artemia and similar freshwater forms • an·os·tra·can\-kən\adjective or noun