1. Of or relating to the bore of a gun (or its ammunition) that measures forty-five hundredths of an inch in diameter
   - .45 caliber [US], .45-caliber [US], .45 calibre [Brit, Cdn]

See also: calibre [Brit, Cdn]

• azygous
• azygous vein
• azymia
• b
• B battery
• B cell
• B complex
• B lymphocyte
• B movie
• B vitamin
• B-52
• B-complex vitamin
• B-flat clarinet
• B-girl
• B-horizon
• b-meson
• B-scan ultrasonography
• B-side
• B. B. King
• B. F. Skinner
• B.O.
• B.Th.U.
• B2B
• B2C
• Ba