[lung] n [ME lunge, fr. OE lungen; akin to OHG lungun lung, lihti light in weight--more at light] (bef. 12c) 1 a: one of the usu. paired compound saccular thoracic organs that constitute the basic respiratory organ of air-breathing vertebrates b: any of various respiratory organs of invertebrates
2. a: a device enabling individuals abandoning a submarine to rise to the surface b: a mechanical device for regularly introducing fresh air into and withdrawing stale air from the lung: respirator -- lung.ful n