/ Dictionary / Index A ascidian: Meaning and Definition of Find definitions for: as•cid•i•an Pronunciation: (u-sid'ē-un), [key] — Zool. Zool. —n. any solitary or colonial tunicate of the class Ascidiacea, exhibiting in the larval stage the vertebrate characteristics of a notocord and hollow nerve cord. —adj. belonging or pertaining to the class Ascidiacea. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ascidian (Thesaurus) asci ascidium Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language