Pronunciation: (kal'u-bur),[key] —n. 1. the diameter of something of circular section, esp. that of the inside of a tube: a pipe of three-inch caliber. 2. Ordn.the diameter of the bore of a gun taken as a unit of measurement.
3. degree of capacity or competence; ability: a mathematician of high caliber. 4. degree of merit or excellence; quality: the high moral caliber of the era.Also,esp. Brit.,cal'i•bre.