A keg is a round container with a flat top and bottom, made of wood in older times and usually of metal now, used for storing and serving beer. It is a kind of small barrel. In pubs and at parties, beer is often pushed out of the keg with gas, so you get draught beer rather than bottles. People also talk about a keg of beer as a unit when they buy drink for a crowd. The word is ordinary and slightly informal — more bar talk than textbook talk. Though actually, keg is smaller in feel than barrel: you say oil barrel, but beer keg. In American college life, keg almost always points to party beer. You can meet a verb too, to keg beer, meaning to put it into kegs, but the everyday word is the container.