barrel // noun [C]
PORK BARREL
1
a large, round container, usually made of wood or metal, with flat ends and, usually, curved sides; the amount that such a container holds
2
a unit of measurement in the oil industry equal to between 120 and 159 litres:
Oil prices rose to $60 a barrel.
The forecast for global oil demand is 76 m barrels a day.
3
a unit of measurement used in the beer-making (brewing) industry equal to about 164 litres