in Commerce, a round vessel bulging in the middle, composed of staves, and bound with hoops. It is chiefly used for holding liquids, particularly ale and beer. The barrel of beer in London formerly contained only 32 ale gallons, = 32½ imperial gallons; but by 43d Geo. III. cap. 69, it was enacted that the barrel of beer should contain 36 gallons, and by 6th Geo. IV. cap. 58, the standard imperial gallon is always to be understood in any excise law where the gallon is mentioned. The barrel therefore contains 36 imperial gallons. (McCulloch's Dict. of Commerce.)

Barrel also denotes a certain weight of several kinds of merchandise, and differs according to the nature of the commodities. Thus a barrel of Essex butter weighs 106 pounds, and of Suffolk butter 256 pounds; a barrel of herrings ought to contain 32 gallons wine-measure, and about 1000 herrings; a barrel of salmon should contain 42 gallons, and a barrel of eels the same; a barrel of soap should weigh 256 lb. The measure of capacity called barrel-bulk = 5 cubic feet.

Mechanics, a term given by watch-makers to the cylinder about which the spring is coiled; and by gunsmiths to the cylindrical tube of a gun, pistol, or blunderbuss, which contains the charge.

Anatomy, the cavity of the tympanum.