Pneumatocyst

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Pneumatocyst \Pneu*mat"o*cyst\, n. [Pneumato- + cyst.] (Zool.)
     A cyst or sac of a siphonophore, containing air, and serving
     as a float, as in Physalia.
     [1913 Webster]