Peak width at peak base intercepted by tangents to the chromatogram drawn at the inflection points on either side of the peak. Represented by the line AB in the peak height figure.
Source:
PAC, 2017, 90, 181. 'Terminology of separation methods (IUPAC Recommendations 2017)' on page 195 (https://doi.org/10.1515/pac-2017-0111)