from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A lid or flap covering an aperture, such as the gill cover in some fishes or the horny shell cover in snails or other mollusks.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A covering flap or lidlike structure in plants and animals, such as a gill cover
from the GNU version of the Collaborative International Dictionary of English
- n. The lid of a pitcherform leaf.
- n. The lid of the urnlike capsule of mosses.
- n. Any lidlike or operculiform process or part.
- n. 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.
- n. The principal opercular bone in the upper and posterior part of the gill cover.
- n. The lid closing the aperture of various species of shells, as the common whelk. See Illust. of Gastropoda.
- n. Any lid-shaped structure closing the aperture of a tube or shell.
from The Century Dictionary and Cyclopedia
- n. A lid or cover; in natural history, a part, organ, or structure which forms a lid, flap, or cover.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. 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
Latin, lid, from operīre, to cover; see wer-4 in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin operire ("to close"). (Wiktionary)