3 Definitions

The closeness of agreement between an observed value and an accepted reference value. Also see Precision
defined by 6SixSigSigma
1. The degree to which an indicated value matches the actual value of a measured variable. 2. In process instrumentation, degree of conformity of an indicated value to a recognized accepted standard value, or ideal value.
defined by Lean Affiliates
Of a measurement, closeness to the real value. "Bias" is the distance from the true value.