Ethylene \Eth"yl*ene\ (-[=e]n), n. [From Ethyl.]

(Chem.) A colorless, gaseous hydrocarbon, C2H4, forming an important ingredient of illuminating gas, and also obtained by the action of concentrated sulphuric acid in alcohol. It is an unsaturated compound and combines directly with chlorine and bromine to form oily liquids (Dutch liquid), -- hence called olefiant gas. Called also ethene, elayl, and formerly, bicarbureted hydrogen.

Source: Webster's Revised Unabridged Dictionary (1913)