1. n. [Geology]

A complex mixture of naturally occurring hydrocarbon compounds found in rock. Petroleum can range from solid to gas, but the term is generally used to refer to liquid crude oil. Impurities such as sulfur, oxygen, and nitrogen are common in petroleum. There is considerable variation in color, gravity, odor, sulfur content, and viscosity in petroleum from different areas.

See: bitumen,  crude oil,  geophysicist,  hydrocarbon,  hydrocarbon kitchen,  maturity,  methane,  natural gas