• synonyms


[oh-pur-kyuh-luh m]
noun, plural o·per·cu·la [oh-pur-kyuh-luh] /oʊˈpɜr kyə lə/, o·per·cu·lums.
  1. Botany, Zoology. a part or organ serving as a lid or cover, as a covering flap on a seed vessel.
  2. Zoology.
    1. the gill cover of fishes and amphibians.
    2. (in many gastropods) a horny plate that closes the opening of the shell when the animal is retracted.
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Origin of operculum

1705–15; < New Latin, Latin: lid, cover, equivalent to oper(īre) to cover + -culum -cule2
Related formso·per·cu·lar, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for operculum

Historical Examples of operculum

  • The operculum fits the entrance to its shell like a trap door.

    Japanese Fairy World

    William Elliot Griffis

  • Sometimes, however, its form is conical or spiral, with or without an operculum.

    The Sea Shore

    William S. Furneaux

  • The outer lip is also thickened and bent inward, and there is no operculum.

    The Sea Shore

    William S. Furneaux

  • In Cryptohelia the cyclosystem is covered by a cap or operculum.

  • This flap, an outgrowth of the hyoid arch, is known as the operculum.

British Dictionary definitions for operculum


noun plural -la (-lə) or -lums
  1. zoology
    1. the hard bony flap covering the gill slits in fishes
    2. the bony plate in certain gastropods covering the opening of the shell when the body is withdrawn
  2. botany the covering of the spore-bearing capsule of a moss
  3. biology any other covering or lid in various organisms
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Derived Formsopercular or operculate (əʊˈpɜːkjʊlɪt, -ˌleɪt), adjective

Word Origin for operculum

C18: via New Latin from Latin: lid, from operīre to cover
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

Word Origin and History for operculum


1713, from Latin operculum "cover, lid," from operire "to cover, close" (see weir), with instrumental suffix *-tlom. Related: Opercular.

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Online Etymology Dictionary, © 2010 Douglas Harper

operculum in Medicine


n. pl. o•per•cu•lums
  1. Something resembling a lid or cover.
  2. The portions of the frontal, parietal, and temporal lobes covering the insula.
  3. The mucus sealing the endocervical canal of the uterus after conception.
  4. The attached flap in cases of torn retinal detachment.
  5. The mucosal flap partially or completely covering an unerupted tooth.
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Related formso•percu•lar (-lər) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

operculum in Science


Plural opercula operculums
  1. A lid or flap covering an opening, such as the gill cover in some fish or the horny flap covering the opening of a snail.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.