cal ‧ i ‧ bra ‧ tion /ˌkæləˈbreɪʃ ə n, ˌkælɪˈbreɪʃ ə n/ BrE AmE noun [uncountable] technical
1 . the process of checking or slightly changing an instrument or tool so that it does something correctly:
the calibration of flight instruments
2 . a set of marks on an instrument or tool used for measuring, or the act of making these marks correct