scy·pho·zo·an 
(sī′fə-zōən)
(sī′fə-zōən)n.
Any of various marine cnidarians of the class Scyphozoa, which includes most of the jellyfishes, characterized by the absence of a polyp stage or by a polyp that is extremely small.
[From New Latin Scyphozōa, class name : Greek skuphos, cup + New Latin -zōa, pl. of -zōon, -zoon.]
scy′pho·zoan adj.