Avoirdupois, Or Averdupois (from the French avoir de pois, goods of weight), the name of a system of weights used in Great Britain and America for all commodities except the precious metals, gems and medicines. The foundation of the system is the grain. A cubic inch of water weighs 252.458 grains. Of this grain 7000 now (see Weights and Measures) make a pound avoirdupois. This pound is divided into 16 oz., and these ounces into 16 drachms.