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.

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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

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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

Those measurements helped rule out other possibilities, such as a distant background star or a brown dwarf whose atmosphere also contained carbon monoxide.

From Science Daily ● Jul. 23, 2026

The first flames would have reacted with the flammable materials to produce carbon monoxide and hydrogen cyanide, often known as the "toxic twins" of fire smoke, he explains.

From BBC ● Jul. 14, 2026

Scientists are also exploring gold catalysts for applications such as removing carbon monoxide from vehicle exhaust and producing propylene oxide, another widely used industrial chemical.

From Science Daily ● Jul. 12, 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

With the apartment windows open, you can taste the carbon monoxide rising from the street below.

From "The Girl on the Train" by Paula Hawkins