1. the internal diameter of a gun barrel or tube
2. the diameter of a bullet or shell
3. the quality or standard of someone’s ability or character

Examples

• The rifle has a .30 caliber barrel.
• Police found several .22 caliber bullets at the scene.
• She is a teacher of the highest caliber.
• We need employees of his caliber to succeed.
• The team showed their true caliber in the championship game.
• This is work of professional caliber.
• Few musicians of that caliber perform in small venues.