a mixture of gaseous hydrocarbons, chiefly methane, occurring naturally in the earth, often in association with petroleum deposits, and piped to cities, factories, etc., to be used as a fuel
See natural gas in American Heritage Dictionary 4
noun Abbr. NG
A mixture of hydrocarbon gases that occurs with petroleum deposits, principally methane together with varying quantities of ethane, propane, butane, and other gases, and is used as a fuel and in the manufacture of organic compounds.