As an adjective hydrozoal
is (zoology) of or pertaining to the hydrozoa.
As a noun hydrozoan is
(biology) any of many colonial coelenterates, of the class hydrozoa , including the hydras, hydroids, hydrocorals, and siphonophores.
hydrozoan
English
Noun
(
en noun)
(biology) Any of many colonial coelenterates, of the class Hydrozoa , including the hydras, hydroids, hydrocorals, and siphonophores.