noun
1. : a looped tubular excretory organ of an entomostracan or the young of many other crustaceans that ends blindly at one extremity and opens to the exterior on or near the second maxilla
2. : a glandular organ in the embryo of many mollusks that secretes the embryonic shell
3. : a specialized glandular part of the oviduct of many animals that forms the egg's shell