# swamp gas

> English word · Noun

## Definitions
1. Gases emitted from a swamp.
2. Hydrogen sulfide.
3. A skeptical explanation that is provided in order to debunk a UFO sighting that a believer regards as ludicrous, illogical or disingenuous.

## Etymology
* (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.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/swamp-gas