crude oil

petroleum as it comes from the ground, before refining.
Also called crude, crude petroleum.

1860–65 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
crude oil
petroleum before it has been refined

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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American Heritage
Science Dictionary
crude oil   (krd)  Pronunciation Key 
Unrefined petroleum.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica

crude oil

mixture of comparatively volatile liquid hydrocarbons (compounds composed mainly of hydrogen and carbon with some nitrogen, sulfur, and oxygen) that occurs in the Earth's crust and is extracted for use as fuel and various petroleum products. Because crude oil is a mixture of widely varying constituents and proportions, its physical properties also vary widely. For example, the specific gravity, as measured on the American Petroleum Institute (API) gravity scale, may range from 10 to more than 60 and the colour from colourless to black. Crude oil occurs underground, at various pressures from tens to hundreds of kilograms per square centimetre, depending on the depth. Because of the pressure, it contains considerable natural gas in solution. The oil underground is much more fluid than it is on the surface, because the elevated temperatures there (on the average, the temperature rises 1 C for every 33 m [108 feet] of depth) decrease the viscosity.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The process can yield crude oil without the contaminating sulfur that much
  petroleum out of the ground contains.
Also called crude oil petroleum field: noun: geographic area whose rock strata
  contain oil or gas.
It has also been investing in refining, since the export tax on petrol and
  diesel is lower than that on crude oil.
Ground-water contamination by crude oil, and other petroleum-based liquids, is
  a widespread problem.
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