- any solitary or colonial tunicate of the class Ascidiacea, exhibiting in the larval stage the vertebrate characteristics of a notocord and hollow nerve cord.
- belonging or pertaining to the class Ascidiacea.
- any minute marine invertebrate animal of the class Ascidiacea, such as the sea squirt, the adults of which are degenerate and sedentary: subphylum Tunicata (tunicates)
- the free-swimming larva of an ascidian, having a tadpole-like tail containing the notochord and nerve cord
- of, relating to, or belonging to the Ascidiacea
