(countable) A round vessel, usually made of wood or metal, with a cylindrical shape, bulging in the middle, and having flat ends, used for storing or transporting liquids or goods.

The quantity which constitutes a full barrel: the volume or weight this represents varies by local law and custom.

A solid drum, or a hollow cylinder or case

A metallic tube, as of a gun, from which a projectile is discharged.

(television) A ceiling-mounted tube from which lights are suspended.

(zoology) The hollow basal part of a feather.

(music) The part of a clarinet which connects the mouthpiece and upper joint, and looks rather like a barrel (1).

(surfing) A wave that breaks with a hollow compartment.

(US, specifically New England) A waste receptacle.

The ribs and belly of a horse or pony.

(biology) Any of the dark-staining regions in the somatosensory cortex of rodents, etc., where somatosensory inputs from the contralateral side of the body come in from the thalamus.

(baseball) A statistic derived from launch angle and exit velocity of a ball hit in play.

(transitive) To put or to pack in a barrel or barrels.

(intransitive) To move quickly or in an uncontrolled manner.

(intransitive) (Discuss(+) this sense) To assume the shape of a barrel; specifically, of the image on a computer display, television, etc., to exhibit barrel distortion, where the sides bulge outwards.