Source : Webster's Revised Unabridged Dictionary (1913)

Pyrosome \Pyr"o*some\, n. [Pyro- + -some body.] (Zo["o]l.)
   Any compound ascidian of the genus {Pyrosoma}. The pyrosomes
   form large hollow cylinders, sometimes two or three feet
   long, which swim at the surface of the sea and are very
   phosphorescent.