1) Aliphatic compound 2) Alkene 3) Olefin 1) Alkene 2) Ethene 3) Ethylene 4) Olefin 
• (n.) Olefiant gas, or ethylene; hence, by extension, any one of the series of unsaturated hydrocarbons of which ethylene is a type. See Ethylene.
O'le·fine noun [ From Olefiant .] (Chemistry) Olefiant gas, or ethylene; hence, by extension, any one of the series of unsaturated hydrocarbons of which ethylene is a type. See Ethylene .