Barrel n. : A round vessel or cask, of greater length than breadth, and bulging in the middle, made of staves bound with hoops, and having flat ends or heads.

Barrel n. : The quantity which constitutes a full barrel. This varies for different articles and also in different places for the same article, being regulated by custom or by law. A barrel of wine is 31/ gallons; a barrel of flour is 196 pounds.

Barrel n. : A solid drum, or a hollow cylinder or case; as, the barrel of a windlass; the barrel of a watch, within which the spring is coiled.

Barrel n. : A metallic tube, as of a gun, from which a projectile is discharged.

Barrel n. : A jar.

Barrel n. : The hollow basal part of a feather.

Barrel v. t. : To put or to pack in a barrel or barrels.

Example:
How is a Barrel roll performed?

Taxonomy
barrel, casks, wine, imperial gallons, container, wooden barrels, Sizes, 1 + 1, Wine barrels, over a barrel, free encyclopedia, kegs, oil, English, liquids, storage container, hoop, firkins.

Defination from the web:
barrel or cask is a hollow cylindrical container, traditionally made of staves (curved wooden members) and bound with iron hoops or rope. The term "barrel" typically refers to wooden vessels that are small enough to be moved by hand, up to puncheon size (see below) ...