operculum

Meanings

1. 1
   noun

   a hard flap or plate that covers an opening in an animal, such as a fish's gills or a snail's shell

   The snail sealed the mouth of its shell with a thick operculum.

2. 2
   noun

   a lidlike part of a moss capsule or fruit that detaches to release spores or seeds

   When the operculum falls away, spores can escape from the moss capsule.

3. 3
   noun

   a flap of gum that partly covers an erupting tooth

   Food trapped beneath the operculum irritated the wisdom tooth.

Borrowed from Latin operculum ("cover, lid"), a diminutive related to operire ("to cover"). Biology and anatomy use it for several structures whose shared function or shape is that of a protective lid.

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