bi·tu·men 
(bĭ-tmən, -ty-, bī-)
(bĭ-tmən, -ty-, bī-)n.
Any of various flammable mixtures of relatively nonvolatile hydrocarbons that occur naturally or are obtained by fractional distillation of petroleum. Bitumens are used for paving, roofing, and waterproofing. Also called asphalt.
[Middle English, mineral pitch from the Near East, from Latin bitūmen, perhaps of Celtic origin and akin to Welsh bedw, birch trees (a common source of pitch).]
bi·tumi·noid′ (-mə-noid′) adj.