(n.) A small opening, perforation, or orifice; a fenestra.

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