operculum

UK: /əʊˈpɜːkjʊləm/ US: (ō pûr′kyə ləm)

Inflections of 'operculum' (n):

opercula

npl

operculums

npl

WordReference Random House Unabridged Dictionary of American English © 2026

o•per•cu•lum  (ō pûr′kyə ləm), n., pl. -la (-lə), -lums. 

1. Botany, Zoology a part or organ serving as a lid or cover, as a covering flap on a seed vessel.
2. Zoology
   • the gill cover of fishes and amphibians. See diag. under fish. 
   • (in many gastropods) a horny plate that closes the opening of the shell when the animal is retracted.

• Neo-Latin, Latin: lid, cover, equivalent. to oper(īre) to cover + -culum -cule²
• 1705–15

o•per′cu•lar, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

operculum / əʊˈpɜːkjʊləm/, opercule / əʊˈpɜːkjuːl/ noun ( -la / -lə/, -lums)

1. the hard bony flap covering the gill slits in fishes
2. the bony plate in certain gastropods covering the opening of the shell when the body is withdrawn
3. the covering of the spore-bearing capsule of a moss
4. any other covering or lid in various organisms

Etymology: 18th Century: via New Latin from Latin: lid, from operīre to cover

oˈpercular, operculate / əʊˈpɜːkjʊlɪt -ˌleɪt/, operculated / əʊˈpɜːkjʊˌleɪtɪd/ adjective