What does "operculum" mean?

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

What is a synonym for "operculum"?

Common synonyms include: cap, cover, lid, stopper, top.

Pronounced //oʊˈpɝ.kjə.ləm//.

//oʊˈpɝ.kjə.ləm// noun

noun ·Uncommon ·Advanced level

Noun

1
A covering flap in animals, such as a gill cover.
"Hyoliths […] have a small, conical calcium carbonate shell, with a lid called an operculum."
2
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 wordnet
3
The lidlike portion of a moss sporangium or of a fruit that detaches to allow the dispersal of spores or seeds.
4
A gum flap covering (part of) a partially erupted tooth, usually a wisdom tooth.
5
A structure which serves as a cover or lid.
"I lifted the circular operculum from its place and laid it carefully on the bale."