Tuns refer to large barrels made of wood or metal that holds liquids like wine, beer, or oil. Synonyms for the word tuns include casks, kegs, barrels, drums, vats, and containers. All these words refer to the same type of vessel and are often used interchangeably. While casks and barrels denote similar sized containers, kegs and drums are smaller in size and capacity. Meanwhile, vats are bigger than tuns and can be used to store larger quantities of liquid. Containers is a broad term that encompasses all types of receptacles that can be used to store or transport liquids and solids.