Word.ws English Dictionary

swamp gas

swamp gas noun: gases emitted from a swamp.

Noun

swamp gas (uncountable)

  1. (literally) Gases emitted from a swamp.
    • Swamp gas occasionally catches fire. Sometimes lightning sets off a patch of swamp gas.
  2. (colloquial) Hydrogen sulfide.
    Synonyms:
    rotten egg gas
  3. (sarcastic) A skeptical explanation that is provided in order to debunk a UFO sighting that a believer regards as ludicrous, illogical or disingenuous.
    • He explained away an especially peculiar sighting with another helping of good old swamp gas.

Synonyms of swamp gas

Origin of swamp gas

* (hydrogen sulfide): So called because it is often emitted from wetlands such as swamps as a result of anaerobic bacteria, and is responsible for their foul “rotten egg” odor. * (ufology): An explanation given by then-skeptic J. Allen Hynek for an alleged UFO sighting in Michigan near Lake Huron in 1966.

Questions about swamp gas

What does swamp gas mean?
Swamp gas means gases emitted from a swamp.
What part of speech is swamp gas?
Swamp gas is a noun.

Words near swamp gas in the dictionary

  1. swamp donkeys
  2. swamp eel
  3. swamp eels
  4. swamp francolin
  5. swamp francolins
  6. swamp gas
  7. swamp gum
  8. swamp gums
  9. swamp harrier
  10. swamp harriers
  11. swamp holly

Source and license

Adapted from Wiktionary: swamp gas (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

Last updated:

Pronunciation audio from Wikimedia Commons, each file under its own free license: LL-Q1860 (eng)-Flame, not lame-swamp gas.wav.

Cite this entry: “swamp gas.” Word.ws, https://word.ws/swamp_gas. Based on Wiktionary, CC BY-SA 4.0.