The term BREW BARREL can be solved by the three-letter word KEG. A KEG is a cylindrical container made of metal or wood, usually used to store and transport beer or other alcoholic beverages. It is also known as a barrel, cask, or tun. The size of a KEG varies depending on the type of beverage it is used for, but it typically holds between 5 and 15 gallons. Kegs are often used in bars and pubs, where they are tapped and served from a tap.