Definition of "Barrel" :

noun: a cylindrical container that holds liquids

noun: a tube through which a bullet travels when a gun is fired

noun: any of various units of capacity

"A barrel of beer is 31 gallons and a barrel of oil is 42 gallons."

noun: the quantity that a barrel (of any size) will hold

noun: a bulging cylindrical shape; hollow with flat ends

verb: put in barrels