Aperture

1. (n.) An opening; a gap, a chasm; an open space; as, an aperture in a wall.

2. (n.) The diameter of the exposed part of the object glass of a telescope or other optical instrument; as, a telescope of four-inch aperture.

Thesaurus Entries

access, aisle, alley, ambulatory, arcade, artery, avenue, bore, breach, break, broaching, cavity, channel, chasm, check, chink, clearing, cleft, cloister, colonnade, communication, conduit, connection, corridor, covered way, crack, crevice, cut, defile, disclosure, discontinuity, exit, fenestra, ferry, fissure, fistula, fontanel, foramen, ford, gallery, gap, gape, gash, gat, gulf, hiatus, hole, hollow, inlet, interchange, intersection, interstice, interval, junction, lacuna, lane, laying open, leak, opening, opening up, orifice, outlet, overpass, pass, passage, passageway, perforation, pinhole, pore, portico, prick, puncture, railroad tunnel, rupture, slash, slit, slot, space, split, stoma, throwing open, traject, trajet, tunnel, uncorking, underpass, unstopping, vent, yawn