A barrel is a large cylindrical container, typically made of wooden staves, which are held together by metal hoops. A barrel is typically designed such that each end is flat, so it is stable while standing upright. However, the sides are convex, so that it can be easily turned from one rolling direction to another by one person.
In modern commerce, a "barrel" is sometimes used as a unit of volume, the size of which depends on the liquid measured. The most common use is in regard to crude oil, where prices and quantities are usually referred to by the barrel. In this context, the barrel equals 42 U.S. gallons of liquid. Beer and wine are sometimes also mentioned in barrels. In those contexts, the volume of a barrel may vary between 31 and 36 gallons.
- The American Heritage® Dictionary of the English Language, 5th Edition.
- U.S. Department of Transportation Maritime Administration