Caliber; Calibre

Part of speech: noun (n.)

1. The diameter of the bore, as a cannon or other firearm, or of any tube; or the weight or size of the projectile which a firearm will carry; as, an 8 inch gun, a 12-pounder, a 44 caliber. The caliber of empty tubes. Reid. A battery composed of three guns of small caliber. Prescott.

2. The diameter of round or cylindrical body, as of a bullet or column.

3. Fig.: Capacity or compass of mind. Burke. Caliber compasses. See Calipers. -- Caliber rule, a gunner's calipers, an instrument having two scales arranged to determine a ball's weight from its diameter, and conversely. -- A ship's caliber, the weight of her armament.