oper·​cu·​lum ō-ˈpər-kyə-ləm How to pronounce operculum (audio)
plural opercula ō-ˈpər-kyə-lə How to pronounce operculum (audio) also operculums
: a body process or part that suggests a lid: such as
: a horny or shelly plate on the posterior dorsal surface of the foot in many gastropod mollusks that closes the shell when the animal is retracted
: the covering of the gills of a fish see fish illustration
: a lid or covering flap (as of a moss capsule)

Examples of operculum in a Sentence

Recent Examples on the Web The electroencephalographic laser-evoked potentials (LEPs) were modelled using six equivalent source dipoles located in the left and right fronto-opercular/anterior-insular cortex, left parietal operculum, left primary somatosensory cortex, medial parietal cortex and left medial temporal cortex. Ncbi Rofl, Discover Magazine, 26 Sep. 2012 The finding of a seizure focus^ in the left frontal operculum, adjacent to the tumor, is consistent^ with the hypothesis that activation of this region by appetite^ triggered seizure activity that then propagated to the surrounding^ cortex and was manifest clinically as a motor seizure. Neuroskeptic, Discover Magazine, 17 Mar. 2010 Scallops, for example, showcase a complex system of camouflage, with a colored shell on top and a white shell on the bottom; most gastropods are born with trapdoor-like devices called an operculum, which protect them from predators. Susan Glaser, cleveland.com, 10 Jan. 2018

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'operculum.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


borrowed from New Latin, going back to Latin, "cover, lid," from operīre "to shut, close, cover" (from op-, variant of ob- ob- + pre-Latin *-wer-je- "open or close," as specified by a prefix, going back to Indo-European *Hu̯er-) + -culum, instrumental suffix (going back to Indo-European *-tlom) — more at aperient

First Known Use

1681, in the meaning defined at sense 1

Time Traveler
The first known use of operculum was in 1681

Dictionary Entries Near operculum

Cite this Entry

“Operculum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/operculum. Accessed 27 May. 2024.

Medical Definition


oper·​cu·​lum ō-ˈpər-kyə-ləm How to pronounce operculum (audio)
plural opercula -lə How to pronounce operculum (audio) also operculums
: any of several parts of the cerebrum bordering the sylvian fissure and concealing the insula
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