• synonyms


See more synonyms for hydroid on Thesaurus.com
  1. noting or pertaining to that form of hydrozoan that is asexual and grows into branching colonies by budding.
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  1. the phase of a hydrozoan coelenterate that consists of polyp forms usually growing as an attached colony.
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Origin of hydroid

First recorded in 1860–65; hydr(a) + -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words


Examples from the Web for hydroid

Historical Examples

  • You see the hydroid does not in the least resemble a jelly-fish.

    Harper's Young People, November 18, 1879


  • Dendroclava, a hydroid, produces the medusa known as Turritopsis.

  • The Hydroid Zoophytes are represented in the first plate by the following examples.


    Charles Kingsley

  • This gigantic creature grows from the small one, called a hydroid, represented in the small cut.

  • Still there were those who would not have grieved had the firm lost its standing in the Hydroid Fibre case.

    The Case and Exceptions

    Frederick Trevor Hill

British Dictionary definitions for hydroid


  1. of or relating to the Hydroida, an order of colonial hydrozoan coelenterates that have the polyp phase dominant
  2. (of coelenterate colonies or individuals) having or consisting of hydra-like polyps
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  1. a hydroid colony or individual
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Word Origin

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

hydroid in Science


  1. 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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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.