arch, arse, bag, barred, bay, bell, breach, break, breech, case, cave, chink, chinked, cleft, close, crack, cut, dawn, fast, flute, fly, gap, grille, hole, latched, leak, lid, locked, mesh, mouth, neck, os, ploy, pore, port, reeve, rent, rip, shut, slit, snag, split, spout, squeeze, string, tab, tear, throat, vent

airing, alcove, anus, bolted, bushing, casing, caution, cervix, chasm, cranny, crater, crevice, crew neck, cutting, dextral, disclosed, doorknob, drawstring, escape, exit, extrude, fissure, fly front, fundus, funnel, gambit, harris, hummer, intake, iris, issue, latchkey, lattice, lunette, mouthless, mouthlike, narrowed, open, outlet, perry, placket, pocket, porta, porthole, prelude, prostyle, red elm, revealed, rima, rondeau, rondel, salpa, scissure, secured, session, skydive, sky dive, sphincter, spreading, squeeze out, stoma, stoppered, strip mall, tank top, teaser, tragus, trimmer, way out, wicket, willow, window

anapsid, aperture, atresia, blastopore, bleeding tooth, bottomless, cardia, cargo hatch, catarrhine, crew neckline, dehiscent, dilater, dilator, discovered, dog collar, doorhandle, drawing string, embrasure, emergence, false glottis, fatiha, fatihah, fenestra, foramen, funnel shape, hiatus, hunting crop, interstice, introitus, kol nidre, micropyle, nonopening, opener, orifice, ostomy, promenade, pylorus, rear of tube, riding crop, scapular, sinistral, stomatal, stomatous, stopped-up, synchroflash, transverse flute, trimmer joist, undermine, ventilate, white cockle, wraparound

acropetal, astomatous, auriculare, basipetal, bladder sphincter, broad-mindedly, colostomy, craniotomy, evening lychnis, exfoliate, fenestella, gastrogavage, gastrostomy, hortensia, imperforate, indehiscent, intonation, keyhole limpet, lychnis alba, myiasis, obturator, operculum, oral fissure, ozark sundrops, pseudoprostyle, rear of barrel, rima oris, roman collar, scapulary, schenectady, slippery elm, sphincter muscle, townsend harris, ulmus rubra, white campion

anapsid reptile, auricular point, bladder campion, catarrhinian, cervix uteri, clerical collar, coelenterate, dissemination, enterostomy, enterotomy, foramen magnum, glottis spuria, hydraulic system, ileostomy, iris diaphragm, jejunostomy, metalworking vise, missouri primrose, oral cavity, peace initiative, porta hepatis, proscenium arch, public exposure, radiator cap, tracheostomy, tracheotomy, uterine cervix, vasoconstrictive, vasoconstrictor, volcanic crater

cnidarian, foramen of monro, matthew calbraith perry, rima vestibuli, salutatorian

anatomical sphincter, atrial septal defect, fissurella apertura, gastroenterostomy, imperforate anus, musculus sphincter vesicae, pulmonary stenosis, salutatory speaker, silene latifolia

diodora apertura, ligamentum teres uteri, rima respiratoria, thoracoepigastric vein, urinary hesitancy, ventricular septal defect

interventricular foramen, oenothera macrocarpa