(Science: chemistry) Pertaining to, or obtained from, apples; as, malic acid. Malic acid, a hydroxy acid obtained as a substance which is sirupy or crystallized with difficulty, and has a strong but pleasant sour taste. It occurs in many fruits, as in green apples, currants, etc. It is levorotatory or dextrorotatory according to the temperature and concentration. An artificial variety is a derivative of succinic acid, but has no action on polarized light, and thus malic acid is a remarkable case of physical isomerism.