n. [ L. bitumen: cf. F. bitume. Cf. Béton. ] 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 ]

. (Photog.) Any process in which advantage is taken of the fact that prepared bitumen is rendered insoluble by exposure to light, as in photolithography. [ Webster 1913 Suppl. ]