calibre

n. (us caliber) 1 a internal diameter of a gun or tube. B diameter of a bullet or shell. 2 strength or quality of character; ability, importance. [french from italian from arabic, = mould]

n. 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.