‖As‐cid″i‐um (ăs‐sĭd″ĭ‐ŭm), n.; pl.Ascidia (–ȧ). [NL., fr. ascus. See Ascus.] 1. (Bot.) A pitcher-shaped, or flask-shaped, organ or appendage of a plant, as the leaves of the pitcher plant, or the little bladderlike traps of the bladderwort (Utricularia).
2. pl.(Zoöl.) A genus of simple ascidians, which formerly included most of the known species. It is sometimes used as a name for the Ascidioidea, or for all the Tunicata.