The Collaborative International Dictionary of English v.0.48:
Doliolum \Do*li"o*lum\, n. [L. doliolum a small cask.] (Zool.) A genus of freeswimming oceanic tunicates, allied to Salpa, and having alternate generations. [1913 Webster]WordNet (r) 3.0 (2006):
doliolum n 1: free-swimming oceanic tunicate with a barrel-shaped transparent body