Definition of operculum
1
: a body process or part that suggests a lid: such as
a
: a horny or shelly plate on the posterior dorsal surface of the foot in many gastropod mollusks that closes the shell when the animal is retracted
b
: the covering of the gills of a fish — see fish illustration
2
: a lid or covering flap (as of a moss capsule)
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Merriam-Webster unabridged
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Time Traveler for operculum
The first known use of operculum was in 1681
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