Source : Webster's Revised Unabridged Dictionary (1913)

Butylene \Bu"ty*lene\, n. [From {Butyl}.] (Chem.)
   Any one of three metameric hydrocarbons, {C4H8}, of the
   ethylene series. They are gaseous or easily liquefiable.

Source : WordNet®

butylene
     n : any of three isomeric hydrocarbons C4H8; all used in making
         synthetic rubbers [syn: {butene}]