GNU Collaborative International Dictionary of English

Found one definition

1.       
   Operculum , n.; pl. L. Opercula , E. Operculums . [L., a cover or lid, fr. operire to cover.]
   (Bot.) (a) The lid of a pitcherform leaf. (b) The lid of the urnlike capsule of mosses.
   1913 Webster
   (Anat.) (a) Any lidlike or operculiform process or part; as, the opercula of a dental follicle. (b) 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. (c) The principal opercular bone in the upper and posterior part of the gill cover.
   1913 Webster
   (Zool.) (a) The lid closing the aperture of various species of shells, as the common whelk. See Illust. of Gastropoda. (b) Any lid-shaped structure closing the aperture of a tube or shell.
   1913 Webster