| a colorless, slightly water-soluble gas, NO, formed by the action of dilute nitric acid on copper, and by the direct combination of atmospheric oxygen and nitrogen at the high temperatures of an electric arc: an intermediate in the manufacture of nitric acid. |
| nitric oxide n. A colorless, poisonous gas, NO, produced as an intermediate during the manufacture of nitric acid from ammonia or atmospheric nitrogen and as a product of cellular metabolism. In the body, nitric oxide is involved in oxygen transport to the tissues, the transmission of nerve impulses, and other physiological activities. |