• WordNet 3.6
    • n operculum a hard flap serving as a cover for (a) the gill slits in fishes or (b) the opening of the shell in certain gastropods when the body is retracted
    • ***
Webster's Revised Unabridged Dictionary
    • Operculum (Zoöl) Any lid-shaped structure closing the aperture of a tube or shell.
    • Operculum (Anat) Any lidlike or operculiform process or part; as, the opercula of a dental follicle.
    • Operculum (Anat) The fold of integument, usually supported by bony plates, which protects the gills of most fishes and some amphibians; the gill cover; the gill lid.
    • Operculum (Zoöl) The lid closing the aperture of various species of shells, as the common whelk. See Illust. of Gastropoda.
    • Operculum (Bot) The lid of a pitcherform leaf.
    • Operculum (Bot) The lid of the urnlike capsule of mosses.
    • Operculum (Anat) The principal opercular bone in the upper and posterior part of the gill cover.
    • ***
Century Dictionary and Cyclopedia
    • n operculum A lid or cover; in natural history, a part, organ, or structure which forms a lid, flap, or cover. Specifically — In botany: In Musci, the lid of the capsule: it covers the peristome, and usually falls off when the spores are ready for dispersion.
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Chambers's Twentieth Century Dictionary
    • n Operculum ō-pėr′kū-lum (bot.) a cover or lid:
    • n Operculum ō-pėr′kū-lum (zool.) the plate over the entrance of a shell: the apparatus which protects the gills of fishes
    • ***


Webster's Revised Unabridged Dictionary
L., a cover or lid, fr. operire, to cover
Chambers's Twentieth Century Dictionary
L.,—operīre, to cover.


In literature:

The pretty wide thin inter-operculum lays freely over the gill membranes, and covers them when shut up.
"Discoveries in Australia, Volume 1." by J Lort Stokes
Cells furnished with a pedunculate operculum.
"Narrative Of The Voyage Of H.M.S. Rattlesnake, Commanded By The Late Captain Owen Stanley, R.N., F.R.S. Etc. During The Years 1846-1850. Including Discoveries And Surveys In New Guinea, The Louisiade Archipelago, Etc. To Which Is Added The Account Of Mr. E.B. Kennedy's Expedition For The Exploration Of The Cape York Peninsula. By John Macgillivray, F.R.G.S. Naturalist To The Expedition. In Two Volumes. Volume 1." by John MacGillivray
The shell is of a yellow horn colour (as is also the operculum) thin and transparent.
"Voyage Of H.M.S. Rattlesnake, Vol. 2 (of 2)" by John MacGillivray
This history was told me, and the nest with its operculum shewn me by the late Dr.
"Zoonomia, Vol. I" by Erasmus Darwin
There is no operculum.
"Marine Protozoa from Woods Hole" by Gary N. Calkins
The distinct operculum in most of the figures would preclude their representing a shark.
"Animal Figures in the Maya Codices" by Alfred M. Tozzer and Glover M. Allen
The capsule, the wall of which bears rudimentary stomata, has a small operculum but no peristome.
"Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3" by Various
Anal operculum: the dorsal arch of the 10th abdominal segment; in caterpillars = supra-anal plate, q.v.
"Explanation of Terms Used in Entomology" by John. B. Smith
Genital orifice covered by an operculum.
"Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 3" by Various
The shell consists of six plates, with an operculum of four valves.
"The New Gresham Encyclopedia. Vol. 1 Part 3" by Various

In news:

Sir—With respect to Einstein's right hemisphere, A M Galaburda agrees with our report that there is no parietal operculum, but suggests that this finding is commonplace.