nitrous oxide

American  

noun

Chemistry, Pharmacology.

1. a colorless, sweet-smelling, sweet-tasting, nonflammable, slightly water-soluble gas, N 2 O, that sometimes produces a feeling of exhilaration when inhaled: used chiefly as an anesthetic in dentistry and surgery, in the manufacture of chemicals, and as an aerosol.

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nitrous oxide British  

noun

1. Systematic name: dinitrogen oxide.  Also called: laughing gas.  a colourless nonflammable slightly soluble gas with a sweet smell: used as an anaesthetic in dentistry and surgery. Formula: N 2 O

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nitrous oxide Scientific  

1. A colorless, sweet-smelling gas. It is used as a mild anesthetic, often called laughing gas. Nitrous oxide occurs naturally in the atmosphere and is a greenhouse gas. Chemical formula: N ₂ O.

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Etymology

Origin of nitrous oxide

First recorded in 1790–1800

Example Sentences

More than 100 maternity staff are taking legal action against a hospital trust after being exposed to "hazardous" levels of nitrous oxide.

From BBC • May 18, 2026

High levels of nitrous oxide in maternity units has affected other hospital trusts across England.

From BBC • May 18, 2026

However the increase in concentrations of heat-trapping greenhouse gases -- carbon dioxide, methane and nitrous oxide -- "to their highest level in at least 800,000 years" has "upset this equilibrium", the WMO said.

From Barron's • Mar. 23, 2026

But excessive tonnages of carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride are changing Earth’s climate.

From The Wall Street Journal • Feb. 24, 2026

Chlorine is green and is deadly; nitrous oxide is colorless and makes people giggle.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife