Source : Webster's Revised Unabridged Dictionary (1913)

Butane \Bu"tane\, n. [L. butyrum butter. See {Butter}.] (Chem.)
   An inflammable gaseous hydrocarbon, C4H10, of the marsh gas,
   or paraffin, series.

Source : WordNet®

butane
     n : occurs in natural gas; used in the manufacture of rubber and
         fuels