outcrop

n (geology 地质) part of a layer (of rock, etc) that can be seen above the surface of the ground （岩层等的）露头（露出地表的部分）.

out of the question, out of touch, out of work, out-, out-and-out, out-of-phase, out-of-shape, out-patient, out-tray, outage, outback, outbid, outboard motor, outbreak, outbuilding, outburst, outcast, outcaste, outclass, outcome, outcry, outdated, outdistance, outdo, outdoor, outdoors, outer, outer space, outermost, outface, outfall, outfield, outfielder, outfight, outfit, outfitter, outflank, outflow, outfox, outgoing,