The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. By extension, any one of the natural hydrocarbons,
      including the hard, solid, brittle varieties called
      asphalt, the semisolid maltha and mineral tars, the oily
      petroleums, and even the light, volatile naphthas.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bitumen
    n 1: any of various naturally occurring impure mixtures of
         hydrocarbons

Easton's 1897 Bible Dictionary:

Bitumen
   Gen. 11:3, R.V., margin, rendered in the A.V. "slime"), a
   mineral pitch. With this the ark was pitched (6:14. See also Ex.
   2:3.) (See SLIME.)