Source : Webster's Revised Unabridged Dictionary (1913)

Bitumen \Bi*tu"men\, n. [L. bitumen: cf. F. bitume. Cf.
   {B['e]ton}.]
   1. Mineral pitch; a black, tarry substance, burning with a
      bright flame; Jew's pitch. It occurs as an abundant
      natural product in many places, as on the shores of the
      Dead and Caspian Seas. It is used in cements, in the
      construction of pavements, etc. See {Asphalt}.

Source : WordNet®

bitumen
     n : any of various naturally occurring impure mixtures of
         hydrocarbons