hydroidPronunciation: /ˈhʌɪdrɔɪd/ ZoologyDefinition of hydroid noun a coelenterate of an order which includes the hydras. They are distinguished by the dominance of the polyp phase. Order Hydroida, class Hydrozoa adjective relating to coelenterates of the hydroid group. another term for polypoid (sense 1).Origin: mid 19th century: from hydra + -oidhydroid in other Oxford dictionaries Definition of hydroid in the US English dictionary
