hydrozoan
noun
hy·dro·zo·an ˌhī-drə-ˈzō-ən 
: 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
hydrozoan adjective
Example Sentences
Recent Examples on the Web The Portuguese man o’ war, or Physalia physalis, is a hydrozoan animal named for its likeness to the Portuguese man of war ships. 
Anjali Huynh, BostonGlobe.com, 9 Aug. 2022 Many 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
Anjali Huynh, BostonGlobe.com, 9 Aug. 2022 Many 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 Word History
Etymology
ultimately from Greek hydr- + zōion animal — more at zoo-
First Known Use
1877, in the meaning defined above
Medical Definition
hydrozoan
noun
hy·dro·zo·an -ˈzō-ən
: any of the class Hydrozoa of coelenterates