noun

1. the size of a bullet or shell as measured by its diameter
2. the diameter of the bore of a gun, usually measured in hundredths of inches or in millimeters
3. the diameter of a cylindrical body or of its hollowed interior
4. degree of worth or value of a person or thing; quality or ability

Etymology: Fr & Sp, ult. < Ar qālib, a mold, last, < Aram < Gr kalopodion, shoemaker's last, lit., little wooden foot < kalon, wood + pous (gen. podos), foot