Mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions minus a true value of the measurand.
Source:
VIM (https://www.iso.org/standard/45321.html)
See also:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2188 (https://doi.org/10.1351/pac199062112167)
PAC, 1995, 67, 1699. 'Nomenclature in evaluation of analytical methods including detection and quantification capabilities (IUPAC Recommendations 1995)' on page 1705 (https://doi.org/10.1351/pac199567101699)