The term 'barrel of ___' can be filled in with three different words: 'LEES, ' 'KEG, ' and 'RIOT.' 'LEES' refers to the sediment that accumulates at the bottom of a barrel or tank during the fermentation process. A 'KEG' is a cylindrical container made of metal, wood, or plastic, typically used to store and transport beer or other alcoholic beverages. Finally, a 'RIOT' is a violent disturbance of the peace by a large crowd of people.