‖n. pl. [ NL., fr. ascidium + -oid. See Ascidium. ] (Zool.) A group of Tunicata, often shaped like a two-necked bottle. The group includes, social, and compound species. The gill is a netlike structure within the oral aperture. The integument is usually leathery in texture. See Illustration in Appendix. [ 1913 Webster ]