Operculum

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Operculum \O*per"cu*lum\, n.; pl. L. {Opercula}, E.
     {Operculums}. [L., a cover or lid, fr. operire to cover.]
     1. (Bot.)
        (a) The lid of a pitcherform leaf.
        (b) The lid of the urnlike capsule of mosses.
            [1913 Webster]


  
     2. (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]
  
     3. (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]

From WordNet (r) 2.0 [wn]:

  operculum
       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
       [also: {opercula} (pl)]