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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.
[From New Latin Hydrozōa, class name : Hydra, type genus; see hydra + -zōa, pl. of -zōon, -zoon.]
(Animals) any colonial or solitary coelenterate of the class Hydrozoa, which includes the hydra, Portuguese man-of-war, and the sertularians
(Animals) of, relating to, or belonging to the Hydrozoa
hy•dro•zo•an(ˌhaɪ drəˈzoʊ ən)
1. any freshwater or marine cnidarian of the classHydrozoa, including attached and free-swimming, often colonial, forms in which the medusa stage is reduced or lacking.adj.
2. belonging or pertaining to the hydrozoans.
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|Noun||1.||hydrozoan - colonial coelenterates having the polyp phase dominant|
cnidarian, coelenterate - radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms
planula - the flat ciliated free-swimming larva of hydrozoan coelenterates
class Hydrozoa, Hydrozoa - coelenterates typically having alternation of generations; hydroid phase is usually colonial giving rise to the medusoid phase by budding: hydras and jellyfishes
hydra - small tubular solitary freshwater hydrozoan polyp
siphonophore - a floating or swimming oceanic colony of polyps often transparent or showily colored
sertularian - feathery colony of long-branched stems bearing stalkless paired polyps