a black, thick, opaque liquid obtained by the destructive distillation of bituminous coal, used in making dyes, medicines, plastics, paints, etc.
See coal tar in American Heritage Dictionary 4
noun
A viscous black liquid containing numerous organic compounds that is obtained by the destructive distillation of coal and used as a roofing, waterproofing, and insulating compound and as a raw material for many dyes, drugs, and paints.