troy unit - any of the unit of the troy system of weights

apothecaries' unit, apothecaries' weight - any weight unit used in pharmacy; an ounce is equal to 480 grains and a pound is equal to 12 ounces

apothecaries' ounce, ounce, troy ounce - a unit of apothecary weight equal to 480 grains or one twelfth of a pound