Ascidium

noun

1. A pitcher-shaped or bottle-shaped part or organ, such as the hollow tubular leaf of a pitcher plant.
2. [Also less prop. <em>Ascidia.</em>] A genus of tunicates, typical of the principal family of the class <em>Ascidia</em>, some of whose species are known as sea-squirts: synonymous with <em>Phallusia.</em>
3. [<em>lowercase</em>; pl. <em>ascidia</em> (-ä).] In <em>botany</em>: Any tubular, horn-shaped, or pitcher-like formation, arising usually from the union of the margins of a leaf or other organ, or from the disproportionate growth of some part.
4. 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).
5. 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.