Webster's Revised Unabridged Dictionary · 1913

olefin

olefin (ō"le*fin or ō"le*fēn) , noun

[From Olefiant.]

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

Also: olefine