hydrozoan Zoology [ ˌhʌɪdrə(ʊ)'zəʊən ]
■ noun a marine invertebrate (coelenterate) of the class Hydrozoa, which includes hydras and Portuguese men-of-war.
■ adjective relating to hydrozoans.
Origin
from mod. L. Hydrozoa , from hydro- + Gk zōion 'animal'.