1) Sea squirt 2) Tunicate 3) Urochord 4) Urochordate 1) Sea squirt 
• (n.) One of the Ascidioidea, or in a more general sense, one of the Tunicata. Also as an adj.
As·cid'i·an noun [ Greek ... bladder, pouch.] (Zoology) One of the Ascidioidea, or in a more general sense, one of the Tunicata. Also as an adj. 
(Gk: askos wine skin; askidion small wineskin) a group of animals that includes seasquirts (Phylum Tunicata; Class Ascidiacea)
[n] - minute sedentary marine invertebrate having a saclike body with siphons through which water enters and leaves
ascidian 1. Minute sedentary marine invertebrate having a saclike body with siphons through which water enters and leaves or 'squirts' out. 2. Known as a 'sea squirt' or a marine invertebrate animal that has a transparent sac-shaped (bag-shaped) body with openings through which water passes in and out. It squirts out a stream of water when disturb...
noun minute sedentary marine invertebrate having a saclike body with siphons through which water enters and leaves