olefin /(ō"lē̇*fĭn [or] ō"lē̇*fēn)/

o·le·fin

olefin

n.
  1. Olefiant gas, or ethylene. See Ethylene. (Chem.) [archaic]
  2. Any one of the series of unsaturated hydrocarbons of which ethylene is the type; a member of the alkene series of hydrocarbons; an alkene. (Chem.)