Definitions

1. noun

The external covering or lid of a bivalve shell or the operculum of a mollusk, especially a snail or slug, which closes the shell or aperture.

“The operculum of the snail helped to seal its shell, protecting it from predators.”

2. noun

A lid or cover, especially one that can be closed or moved to cover or reveal a part.

“The operculum of the camera lens helped to protect it from dust and debris.”