a translucent, gummy, amorphous substance, nearly tasteless and odorless, used as a substitute for gum, for sizing, etc., and obtained from starch by the action of heat, acids, or diastase. it is of somewhat variable composition, containing several carbohydrates which change easily to their respective varieties of sugar. it is so named from its rotating the plane of polarization to the right; -- called also british gum, alsace gum, gommelin, leiocome, etc. see achroodextrin, and erythrodextrin.