yawn, aperture, broaching, cavity, chasm, check, clearing, cleft, crack, dehisce, dehiscence, disclosure, doldrums, doze, drowse, ennui, fenestra, fistula, fontanel, foramen , gap, gape, gaping, gat, gulf, hang open, hiatus, hole, hollow, inlet, interval, lacuna, laying open, leak, nap, opening, opening up, orifice, oscitancy, oscitate, oscitation, outlet, pandiculation, passageway, pore, slot, snooze, space, split, stoma, the gapes, throwing open, uncorking, unstopping, yaw, yawning