Source : Webster's Revised Unabridged Dictionary (1913)

Octane \Oc"tane\, n. [See {Octa-}] . (Chem.)
   Any one of a group of metametric hydrocarcons ({C8H18}) of
   the methane series. The most important is a colorless,
   volatile, inflammable liquid, found in petroleum, and a
   constituent of benzene or ligroin.

Source : WordNet®

octane
     n : any isomeric saturated hydrocarbon found in petroleum and
         used as a fuel and solvent