caliber

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The diameter of the inside of a round cylinder, such as a tube.
2. n. The diameter of the bore of a firearm, usually shown in hundredths or thousandths of an inch and expressed in writing or print in terms of a decimal fraction: .45 caliber.
3. n. The diameter of a large projectile, such as an artillery shell, measured in millimeters or in inches.
4. n. Degree of worth; quality: a school of high caliber; an executive of low caliber.

Century Dictionary and Cyclopedia

1. n. The diameter of a body, especially of the hollow inside of a cylinder: as, the caliber of a piece of ordnance or other firearm. In the United States the caliber of a firearm is expressed in decimal parts of an inch; thus, a rifle of .44-inch caliber (often shortened to “a 44-caliber rifle,” “a 32-caliber pistol,” etc.); of a cannon, either by the diameter of its bore, as a 10-inch gun, or by the weight of a solid round shot which it can carry, as a 12-pounder. In Great Britain the calibers of small arms are commonly expressed in decimal parts of an inch; of field-guns, by the weight of a solid round shot which will fit the bore, as a 6-pounder; of heavy guns, in tons, as a 38-ton gun or a 100-ton gun. In France and in other countries on the continent the caliber is expressed in millimeters or centimeters.
2. n. Figuratively, compass or capacity of mind; the extent of one's intellectual endowments.
3. n. In horology: The distance between the two plates of a watch which determines the flatness of the movement.
4. n. The plate upon which is traced the arrangement of the pieces of a clock; the pattern-plate.
5. In gunnery, to ascertain the caliber of; calibrate. See caliper.

Wiktionary

1. n. US spelling of calibre.

GNU Webster's 1913

1. n. (Gunnery) 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.
2. n. The diameter of round or cylindrical body, as of a bullet or column.
3. n. Fig.: Capacity or compass of mind.

WordNet 3.0

1. n. a degree or grade of excellence or worth
2. n. diameter of a tube or gun barrel