marsh gas marsh foxtail • marsh grass · · · Info · Definitions · Synonyms · Characters · · marsh gas · · Text Common · · Latin · · Scripts 9 · · Length Definitions · · · (noun) methane gas produced when vegetation decomposes in water. · · Noun Definition 1 Synonyms · · · marsh · · Synonym 1 marshland · · Synonym 2 fen · · Synonym 3 fenland · · Synonym 4 Characters · · space U+0020 a latin small letter a U+0061 g latin small letter g U+0067 h latin small letter h U+0068 m latin small letter m U+006D r latin small letter r U+0072 s latin small letter s U+0073