Pronunciation: (ō-pûr'kyu-lum), [key]
—pl. -laPronunciation: (-lu), [key] -lums.
1. Bot., Zool.a part or organ serving as a lid or cover, as a covering flap on a seed vessel.
a. the gill cover of fishes and amphibians. See diag. under fish.
b. (in many gastropods) a horny plate that closes the opening of the shell when the animal is retracted.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.