(n) the act of checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument, Syn. standardisation, standardization, Example:the thermometer needed calibration
The Collaborative International Dictionary of English (GCIDE) v.0.53 Collaborative International Dictionary (GCIDE)
n. The process of estimating the caliber a tube, as of a thermometer tube, in order to graduate it to a scale of degrees; also, more generally, the determination of the true value of the spaces in any graduated instrument. [ 1913 Webster ]