Orifice

(n.) A mouth or aperture, as of a tube, pipe, etc.; an opening; as, the orifice of an artery or vein; the orifice of a wound.

Thesaurus Entries

aperture, broaching, cavity, chasm, check, clearing, cleft, crack, disclosure, fenestra, fistula, fontanel, foramen, gap, gape, gat, gulf, hiatus, hole, hollow, inlet, interval, lacuna, laying open, leak, opening, opening up, outlet, passageway, pore, slot, space, split, stoma, throwing open, uncorking, unstopping, vent, yawn