any of a subphylum (Tunicata) of solitary or colonial sea chordates, having a saclike body enclosed by a thick tunic, including the salps and ascidians
See tunicate in American Heritage Dictionary 4
(to͞oˈnĭ-kĭt, -kātˌ, tyo͞oˈ-)
noun
Any of various chordate marine animals of the subphylum Tunicata or Urochordata having a cylindrical or globular body enclosed in a tough outer covering and including the sea squirts and salps.