/ Dictionary / Index O operculum: Meaning and Definition of Find definitions for: o•per•cu•lum Pronunciation: (ō-pûr'kyu-lum), [key] — pl. -la -lums. a part or organ serving as a lid or cover, as a covering flap on a seed vessel. the gill cover of fishes and amphibians. See diag. underfish. (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. See also: operculum (Thesaurus) operculate opere citato* Related Content Daily Word Quiz: inutiae Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language