n. - Any lidlike or operculiform process or part; as, the
opercula of a dental follicle.
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.