(biochemistry) A large beta sheet that twists and coils to form a closed structure in which the first strand is hydrogen-bonded to the last.

(military, historical) An empty powder barrel pierced with holes and filled with shavings soaked in pitch, used to light up a ditch or a breach.

A measure equal to five cubic feet, used in estimating capacity, as of a vessel for freight.

(fisheries) A barrel nearly full of split mackerel, loosely put in, and afterward filled with salt water in order to soak the blood from the fish before salting.

(metalworking) A process of extracting gold or silver by treating the ore in a revolving barrel or drum, with mercury, chlorine, cyanide solution, or other reagent.

Someone who plays a barrel organ.

plural of barrel drum

(music) A drum (membranophone) with a shape that bulges in the middle, forming a barrel-like appearance, usually very large and made of wood with a one-headed and open-bottomed body.

a barrel filled with explosives, used as an improvised unguided bomb and dropped from a helicopter or airplane

(figuratively) A very cheery and happy person.