A barrel (sometimes called a cask) was a cylindrical portable storage container that is made out of wood or metal.
In the year 2268, Cervantes Quinn had to dive behind some barrels for cover while trying to avoid fire from the Nausicaan bounty hunter Kajek. (VAN - Declassified novella: The Stars Look Down)
Barrels on Caldonia III were used to collect water. (DS9 comic: "For the Glory of the Empire")