pe·tro·le·um (p?-tr??l?-?m)n. A thick, flammable, yellow-to-black mixture of gaseous, liquid, and solid hydrocarbons that occurs naturally beneath the earth’s surface, can be separated into fractions including natural gas, gasoline, naphtha, kerosene, fuel and lubricating oils, paraffin wax, and asphalt and is used as raw material for a wide variety of derivative products.[Middle English, from Medieval Latin petr?leum : Latin petra, rock; see petrous + Latin ?leum, oil; see oil.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.petroleum (p??tr??l??m) n (Elements & Compounds) a dark-coloured thick flammable crude oil occurring in sedimentary rocks around the Persian Gulf, in parts of North and South America, and below the North Sea, consisting mainly of hydrocarbons. Fractional distillation separates the crude oil into petrol, paraffin, diesel oil, lubricating oil, etc. Fuel oil, paraffin wax, asphalt, and carbon black are extracted from the residue[C16: from Medieval Latin, from Latin petra stone + oleum oil]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014pe?tro?le?um (p??tro? li ?m) n. an oily, thick, flammable, usu. dark-colored liquid that is a form of bitumen or a mixture of various hydrocarbons, occurring naturally and commonly obtained by drilling: used as fuel, or separated by distillation into gasoline, naphtha, benzene, kerosene, paraffin, etc. [1520?30;