: any of a class (Hydrozoa) of cnidarians (such as the hydra, fire coral, and Portuguese man-of-war) that includes solitary and colonial polyps and medusae but often having the medusa stage reduced or absent and lacking nematocysts in the digestive cavity — see siphonophore
Recent Examples on the WebMany living things, including strawberries, orchids and some jellyfish cousins called hydrozoans, propagate this way today.
Cara Giaimo, New York Times, 6 Mar. 2020 The creatures, which are marine hydrozoans and relatives of jellyfish, have recently been spotted on Sullivan’s Island and in Hilton Head.
USA TODAY, 10 June 2019
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hydrozoan.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.