Operculum1. (n.) The lid of a pitcherform leaf.
2. (n.) The lid of the urnlike capsule of mosses.
3. (n.) Any lidlike or operculiform process or part; as, the opercula of a dental follicle.
4. (n.) The fold of integument, usually supported by bony plates, which protects the gills of most fishes and some amphibians; the gill cover; the gill lid.
5. (n.) The principal opercular bone in the upper and posterior part of the gill cover.
6. (n.) The lid closing the aperture of various species of shells, as the common whelk.
7. (n.) Any lid-shaped structure closing the aperture of a tube or shell.
Thesaurus Entries
Balmoral, Dutch cap, Panama, Panama hat, Salvation Army bonnet, Stetson, acme, apex, apogee, ascender, astrakhan, back, balaclava helmet, baseball cap, bastard type, beany, beard, bearskin, beaver, befog, belly, beret, best, better, bevel, bewilder, black letter, blanket, blasting cap, boater, body, bonnet, boot, bowler, bracket capital, brass hat, breech, brow, busby, button up, calash, campaign hat, cap, capital, capote, capsheaf, caput, carry to completion, case, castor, ceil, chapeau, chapeau bras, clean up, climax, cloak, cloche, close out, close up, cloud nine, coat, cob, cock-and-pinch, coif, complete, conclude, confound, confuse, consummate, cork, cornice, counter, cover, coverchief, coxcomb, crest, crown, culmen, culminate, culmination, derby, descender, detonating powder, detonator, dome, edge, electric detonator, em, en, end, exceed, excel, exploder, extreme limit, extremity, face, fantail, fat-faced type, feet, fez, finalize, finish, finish off, finish up, font, frock, frost, fulminating mercury, fuse, get done, get it over, get through, get through with, give in kind, go one better, gown, groove, handkerchief, hard hat, hat, head, headcloth, headdress, headgear, heading, headpiece, headtire, headwear, heaven, heavens, height, helmet, high noon, highest pitch, highest point, homburg, hood, ice, improve on, italic, jacket, jockey cap, kaffiyeh, kelly, kepi, kerchief, leghorn, letter, lex talionis, lid, ligature, limit, logotype, lower case, majuscule, mantle, match, maximum, mercury fulminate, meridian, millinery, minuscule, mobcap, mop up, mortarboard, mountaintop, ne plus ultra, nick, nightcap, no place higher, noon, opera hat, operculum, outshine, outstrip, outtop, outweigh, overarch, overbalance, overbear, overcast, overcome, overlay, overpass, overseas cap, overspread, overtop, pass, peak, peaked cap, percussion cap, perfect, perplex, pi, pica, picture hat, pillbox, pinhead, pinnacle, pitch, pith hat, pith helmet, plug, point, poke, pole, porkpie, pose, predominate, preponderate, prevail, primacord, primer, priming, print, puggree, repay in kind, return the compliment, return the like, ridge, roman, roof, roof in, round out, rumal, sailor, sans serif, scraper, script, seventh heaven, shank, shirt, shoe, shoulder, shovel hat, silk hat, skullcap, sky, slouch hat, small cap, small capital, snood, sock, sombrero, spire, squib, stamp, stem, stocking, stopper, stovepipe, stumble, summit, sun hat