barrel

(bărˈəl)

1. A large cylindrical container, usually made of staves bound together with hoops, with a flat top and bottom of equal diameter.
2. The quantity that a barrel with a given or standard capacity will hold.
3. Abbr. bar. or bbl. or bl. Any of various units of volume or capacity. In the U.S. Customary System it varies, as a liquid measure, from 31 to 42 gallons (120 to 159 liters) as established by law or usage. See Table at measurement.
4. The cylindrical part or hollow shaft of any of various mechanisms, as:
   a. The metal, cylindrical part of a firearm through which the bullet travels.
   b. A cylinder that contains a movable piston.
   c. The drum of a capstan.
   d. The cylinder within the mechanism of a timepiece that contains the mainspring.
5. The trunk of a quadruped animal, such as a horse or cow.
6. Informal A large quantity: a barrel of fun.
7. Slang An act or instance of moving rapidly, often recklessly, in a motor vehicle.