\Pe*tro"le*um\, n. [NL., fr. L. petra a rock + oleum
oil: cf. F. p['e]trole. Cf. {Petrify}, and {Oil}.]
Rock oil, mineral oil, or natural oil, a dark brown or
greenish inflammable liquid, which, at certain points, exists
in the upper strata of the earth, from whence it is pumped,
or forced by pressure of the gas attending it. It consists of
a complex mixture of various hydrocarbons, largely of the
methane series, but may vary much in appearance, composition,
and properties. It is refined by distillation, and the
products include kerosene, benzine, gasoline, paraffin, etc.
{Petroleum spirit}, a volatile liquid obtained in the
   distillation of crude petroleum at a temperature of
   170[deg] Fahr., or below. The term is rather loosely
   applied to a considerable range of products, including
   benzine and ligroin. The terms petroleum ether, and
   naphtha, are sometimes applied to the still more volatile
   products, including rhigolene, gasoline, cymogene, etc.