[ hahy-droid ]
/ ˈhaɪ drɔɪd /


noting or pertaining to that form of hydrozoan that is asexual and grows into branching colonies by budding.


the phase of a hydrozoan coelenterate that consists of polyp forms usually growing as an attached colony.

Origin of hydroid

First recorded in 1860–65; hydr(a) + -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for hydroid

British Dictionary definitions for hydroid

/ (ˈhaɪdrɔɪd) /


of or relating to the Hydroida, an order of colonial hydrozoan coelenterates that have the polyp phase dominant
(of coelenterate colonies or individuals) having or consisting of hydra-like polyps


a hydroid colony or individual

Word Origin for hydroid

C19: from hydra + -oid
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for hydroid

[ hīdroid′ ]

Any of numerous, usually colonial marine cnidarians, having a polyp rather than a medusoid form as the dominant stage of the life cycle. Hydroids have a simple cylindrical body with a mouthlike opening surrounded by tentacles. Most species form colonies with individual hydroids branching off from a common hollow tube that is probably used to share ingested food. The young develop from eggs or from buds. The most well-known hydroids are the hydras (genus Hydra), which are atypical in being both freshwater and solitary.
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