o·le·fin (ō'lə-fĭn) n. Any of a class of unsaturated open-chain hydrocarbons such as ethylene, having the general formula CnH2n; an alkene with only one carbon-carbon double bond.
[French (gaz) oléfiant, oil-forming (gas), ethylene : Latin oleum, oil; see oil + French -fiant, present participle of -fier, -fy.] o'le·fin'ic adj.
olefin o·le·fin (ō'lə-fĭn) n. Any of a group of unsaturated open chain hydrocarbons possessing one or more double bonds, the simplest of which is ethylene.