It is made by reacting ammonia with oxygen with a catalyst. It is also made in lightning. It can be made in small amounts by reacting copper with nitric acid. It can also be made by reducing nitrous acid with compounds such as iron(II) sulfate.
It is used in making nitric acid from ammonia. The ammonia is reacted with air to make nitric oxide. The nitric oxide is oxidized to nitrogen dioxide by air. The nitrogen dioxide is dissolved in water to make nitric acid and more nitric oxide.
It is also used as a stimulant in the human body. It has many actions in the human body that are being studied.
Nitric oxide is toxic when breathed in. It also easily is oxidized to nitrogen dioxide, a toxic brown choking substance.