nitric oxide

American  

noun

Chemistry.

1. 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.

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nitric oxide British  

noun

1. Systematic name: nitrogen monoxide.  a colourless slightly soluble gas forming red fumes of nitrogen dioxide in air. Formula: NO

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nitric oxide Scientific  

1. A colorless, poisonous gas produced as an intermediate compound during the manufacture of nitric acid from ammonia or from atmospheric nitrogen. It is also produced through cellular metabolism. In the body, nitric oxide is involved in oxygen transport to the tissues, the transmission of nerve impulses, and other physiological activities. Chemical formula: NO.

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Closer Look

While nitric oxide (NO) was once regarded solely as a poisonous air pollutant, responsible for the formation of photochemical smog and acid rain leading to the destruction of the ozone layer, today it is also appreciated as a molecule essential to human health. Nitric oxide is the first gas discovered to act as a signaling molecule, a transmitter of important signals to cells in various systems of the human body. Even though NO continues to be detrimental to the environment, it was heralded as Science Magazine's Molecule of the Year in 1992, and the Nobel Prize for physiology or medicine was awarded in 1998 to the three scientists who discovered that NO works as a signaling molecule in the cardiovascular system. It is now known that the cells of a blood vessel's inner walls use NO to signal the vessel to relax and dilate, increasing blood flow. Nitroglycerin, whose effectiveness in treating heart problems was once a mystery, is now known to work by releasing NO. NO has a variety of other important biological functions, including destroying bacteria within the immune system and acting as a neurotransmitter.

Etymology

Origin of nitric oxide

First recorded in 1800–10

Example Sentences

When the balance of oral bacteria shifts in the wrong direction, that nitrate to nitric oxide pathway may become less efficient.

From Science Daily • May 25, 2026

It found that chlorhexidine, an antiseptic mouthwash, disrupted nitrate processing and reduced gastric nitric oxide synthesis, while dietary nitrate supplementation partly preserved microbial function and nitric oxide related signaling during antiseptic use.

From Science Daily • May 25, 2026

Researchers focused on two naturally occurring watermelon compounds, L-citrulline and L-arginine, which are involved in nitric oxide production.

From Science Daily • May 17, 2026

In a complementary strategy, the scientists engineered a modified version of the TSC2 protein that resists nitric oxide related modification.

From Science Daily • Mar. 7, 2026

Among its old pupils was included Sir Humphry Davy, born in 1778, the eminent chemist who was the first to employ the electric current in chemical decomposition and to discover nitric oxide or "laughing gas."

From From John O'Groats to Land's End by Naylor, Robert