Definition of: operculum

(ō·pûr′ky·ləm) noun plural ·la (-lə) Biol.
1. A lid, cover, or lidlike part or organ, as of the orifice of the capsule in mosses, of certain capsules (as a pyxis) in flowering plants, of the hair follicles, etc.
2. A horny or shelly plate in many gastropods, serving to close the aperture when the animal is retracted.
3. In fishes, the gill cover; specifically, the hindmost and uppermost bone of the gill cover.
4. In the king crab, the plate that covers the abdominal limbs.
5. The labrum of certain dipterous insects.
6. A part of the cerebral cortex. Also o·per·cele (ō·pûr′sēl), o·per′·cule (-kyl). [<L, a covering, lid <operire cover]
—o·per′cu·lar adjective
—o·per′cu·late, o·per′cu·lat′ed adjective