the diameter of something of circular section, especially that of the inside of a tube:
a pipe of three-inch caliber.
Ordnance. the diameter of the bore of a gun taken as a unit of measurement.
degree of capacity or competence; ability:
a mathematician of high caliber.
degree of merit or excellence; quality:
the high moral caliber of the era.
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Blackwood’s Edinburgh Magazine, No. 401, March 1849 Various
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the diameter of a cylindrical body, esp the internal diameter of a tube or the bore of a firearm
the diameter of a shell or bullet
ability; distinction: a musician of high calibre
personal character: a man of high calibre
n. Historical Examples The Chronicles of Newgate, vol. 1/2 Arthur Griffiths