(1):

(n.) A narrow-necked vessel of metal or glass, used for various purposes; as of sheet metal, to carry gunpowder in; or of wrought iron, to contain quicksilver; or of glass, to heat water in, etc.

(2):

(n.) The wooden or iron frame which holds the sand, etc., forming the mold used in a foundry; it consists of two or more parts; viz., the cope or top; sometimes, the cheeks, or middle part; and the drag, or bottom part. When there are one or more cheeks, the flask is called a three part flask, four part flask, etc.

(3):

(n.) A small bottle-shaped vessel for holding fluids; as, a flask of oil or wine.

(4):

(n.) A bed in a gun carriage.