A hole to admit or discharge air; specifically, a spot in the ice not frozen over. [1913 Webster]
A fault in a casting, produced by a bubble of air; a blowhole. [1913 Webster]
A local region in the atmosphere having a downward movement and offering less than normal support for the sustaining surfaces of a flying machine, causing an airplane to drop suddenly. Same as air pocket. [Webster 1913 Suppl.]

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THESAURUS

air hole

CAT, aerospace, aerosphere, air duct, air passage, air pocket, air shaft, air tube, airspace, airway, armhole, blowhole, breathing hole, bullet-hole, bump, bunghole, ceiling, cringle, crosswind, deadeye, empty space, eye, eyelet, favorable wind, fog, front, gasket, grommet, guide, head wind, high-pressure area, hole, ionosphere, jetstream, keyhole, knothole, loop, loophole, louver, louverwork, low-pressure area, manhole, mousehole, naris, nostril, overcast, peephole, pigeonhole, pinhole, placket, placket hole, pocket, porthole, punch-hole, roughness, shaft, soup, space, spilehole, spiracle, stratosphere, substratosphere, tail wind, tap, touchhole, transom, tropopause, troposphere, trough, turbulence, vent, ventage, venthole, ventiduct, ventilating shaft, ventilator, visibility, visibility zero, wind tunnel

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