Natural wine. The product of the juice or must of sound, ripe grapes or other sound, ripe fruit (including berries) made with any cellar treatment authorized by subparts F and L of this part and containing not more than 21 percent by weight (21 degrees Brix dealcoholized wine) of total solids.
27 CFR § 24.10
When used in this part and in the forms prescribed under this part, terms will have the meanings ascribed in this section. Words in the plural form also include the singular, and vice versa, and words indicating the masculine gender also include the feminine. The terms includes and including do not exclude items not enumerated which are in the same general class. The definitions in this section do not supersede or affect the requirements of part 4 of this chapter, relative to the labeling of wine under the provisions of the Federal Alcohol Administration Act (49 Stat. 981; 27 U.S.C. 205).