of a class (Hydrozoa) of cnidarians having a saclike body consisting of two layers of cells, and a mouth that opens directly into the body cavity
Origin of hydrozoan; from Modern Latin Hydrozoa ; from hydra + zo- + -an
any animal of this class, as a hydroid or Portuguese man-of-war
Any of various cnidarians of the class Hydrozoa, including the hydras, hydroids, and siphonophores, which exhibit alternation of generations between the polyp and medusa stage or exist in only one or the other stage.
Origin of hydrozoanFrom New Latin Hydroz&omacron;a, class name : Hydra, type genus; see hydra + -z&omacron;a, pl. of -z&omacron;on, -zoon.