operculum

Etymology

Borrowed from Latin operculum.

noun

1. (zoology) A covering flap in animals, such as a gill cover.
   Hyoliths […] have a small, conical calcium carbonate shell, with a lid called an operculum. 18 January 2017, Susannah Lydon, The Guardian
2. (botany) The lidlike portion of a moss sporangium or of a fruit that detaches to allow the dispersal of spores or seeds.
3. (dentistry) A gum flap covering (part of) a partially erupted tooth, usually a wisdom tooth.
4. A structure which serves as a cover or lid.
5. (anatomy) One of several flaps of cerebral cortex covering the insula.