ōˈpərkyələm noun
( plural opercu·la -lə ; also oper·culums )
Etymology: New Latin, from Latin, cover, lid, from operire to cover, shut (from op-, ob to, before + — assumed — verire to shut) + -culum, suffix denoting instrument — more at epi- , weir
1. : a lid or covering flap (as of a moss capsule, of an ascus, of a pyxidium in a seed plant, or of the pitcher in some pitcher plants)
2. : a part of the cerebrum bordering the lateral fissure and concealing the island of Reil
3. : a body process or part that suggests a lid: as
a. : the horny or shelly plate that develops on the posterior dorsal surface of the foot in many gastropod mollusks (as in Streptoneura) and serves to close the shell when the animal is retracted
b. : the two or more movable plates of the shell of a barnacle
c. : the first pair of abdominal appendages of a king crab which are united and cover the other pairs
d. : one of the small plates covering the orifice of a trachea or lung sac in a spider
e. : the fold of integument usually supported by bony plates that protects the gills in most fishes and some amphibians : gill cover — see fish illustration
f. : the principal bony plate of the gill cover : opercle
g. : a flap that covers the mouth of some bryozoans
h. : a circular lid at one end of the egg of various invertebrates