- 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 diameter of round or cylindrical body, as of a bullet
or column. - Fig.: Capacity or compass of mind.
Meaning of 'calibre' (Princeton's WordNet)
1 . calibre
[ n]
Meaning (1): - a degree or grade of excellence or worth