1. any of the intervals into which a range of diameters of tree stems or logs may be divided for classification and use —note e.g., the 6-in (15.24-cm) diameter class includes diameters from 5.0 to 6.9 in (12.70 to 17.52 cm) 2. the actual trees or logs falling into such an interval —see stem classThis definition last updated 10/25/2008