— petroleous , adj.
/peuh troh"lee euhm/ , n.
an oily, thick, flammable, usually dark-colored liquid that is a form of bitumen or a mixture of various hydrocarbons, occurring naturally in various parts of the world and commonly obtained by drilling: used in a natural or refined state as fuel, or separated by distillation into gasoline, naphtha, benzene, kerosene, paraffin, etc.
[ 1520-30; petr ( a ) rock ( pétra ) + oleum OIL ]