In petrography, in the quantitative classification of igneous rocks (see rock), having the character of or producing a variety of a mode.In biology, having the character of a zoölogical or botanical variety; subspecific, or of the character of a subspecies; racial, with reference to geographical variation; of or pertaining to varieties: variational: as, varietal characters; varietal differences or distinctions. See variability, 2. variation, 8, and variety, 6.