carbon monoxide

American  

noun

1. a colorless, odorless, poisonous gas, CO, that burns with a pale-blue flame, produced when carbon burns with insufficient air: used chiefly in organic synthesis, metallurgy, and in the preparation of metal carbonyls, as nickel carbonyl.

---

carbon monoxide British  

noun

1. a colourless odourless poisonous flammable gas formed when carbon compounds burn in insufficient air and produced by the action of steam on hot carbon: used as a reducing agent in metallurgy and as a fuel. Formula: CO

---

Etymology

Origin of carbon monoxide

First recorded in 1870–75

Compare meaning

How does carbon-monoxide compare to similar and commonly confused words? Explore the most common comparisons:

• carbon monoxide vs. carbon dioxide

Example Sentences

See Examples For:

carbon monoxide

EPA officials said on a call Monday that the change will not include pollutants that directly harm health such as carbon monoxide and nitrogen dioxide, which are regulated separately.

From Los Angeles Times ● Sep. 14, 2026

Emissions of carbon monoxide, nitrous oxide and dangerous particulate matter increased by 196%, 111%, and 139% respectively.

From The Wall Street Journal ● Sep. 7, 2026

The researchers combined molecular nitrogen, ammonia, carbon dioxide, and carbon monoxide.

From Science Daily ● Sep. 2, 2026

State media initially reported four deaths and dozens trapped after levels of carbon monoxide -- a highly toxic, odourless gas -- in the mine were found to have "exceeded limits".

From Barron's ● May 23, 2026

It didn't look much like a factory—no towering steel silos or smokestacks billowing carbon monoxide, just a few buildings that vaguely reminded him of airplane hangars.

From "An Abundance of Katherines" by John Green