marsh gas

American  

noun

1. a gaseous decomposition product of organic matter, consisting primarily of methane.

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marsh gas British  

noun

1. a hydrocarbon gas largely composed of methane formed when organic material decays in the absence of air

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Etymology

Origin of marsh gas

An Americanism dating back to 1775–85

Example Sentences

The simplest of these is methane, or marsh gas, which is formed in nature by the bacterial decomposition of organic matter under water.

From The New Yorker • Jan. 3, 2017

Are these pans as lethal as marsh gas?

From The Guardian • Aug. 13, 2011

Newton's muted trumpet line hovers in the air like marsh gas; White's minor piano chords walk the listener towards the fateful spot; then, at last, there's Holiday.

From The Guardian • Feb. 16, 2011

Rumors, hysteria, gloom, mockery emanated from the general boredom like marsh gas from a swamp.

From Time Magazine Archive

The layer of muck had small holes all over it, where marsh gas breathed out.

From "Root Magic" by Eden Royce