What is the meaning of Operculum?

A covering flap in animals, such as a gill cover.

The lidlike portion of a moss sporangium or of a fruit that detaches to allow the dispersal of spores or seeds.

A gum flap covering (part of) a partially erupted tooth, usually a wisdom tooth.

A structure which serves as a cover or lid.

One of several flaps of cerebral cortex covering the insula. (clarification of this definition is needed)

cover, covering

Source: wiktionary.org