Pe-trō'le-ūm, n.

(124), n. [N. Lat., from Lat. petra, rock, and oleum, oil; Sp. petroleo, It. petrolio, Fr. pétrole.] Rock oil, a liquid, inflammable, bituminous substance exuding from the earth and collected on the surface of the water in wells and fountains, in various parts of the world, or oozing from cavities in rocks. It is essentially composed of carbon and hydrogen. Fourcroy. Kirwan.