Definition of: petroleum

(pə·trō′lē·əm) noun
An oily, liquid mixture of numerous hydrocarbons, chiefly of the paraffin series, found in many widely scattered subterranean deposits, and extensively used for heat and light. A number of very important substances are obtained by the fractional distillation of petroleum, such as petroleum ether, gasoline, naphtha, benzine, kerosene, paraffin, etc. [<Med. L <L petra a rock (<Gk.) + oleum oil]