av·oir·du·pois / ˌävərdəˈpoiz/ • n. a system of weights based on a pound of 16 ounces or 7,000 grains, widely used in English-speaking countries: [as adj.] avoirdupois weights | a pound avoirdupois. Compare with troy. ∎ humorous weight; heaviness.

avoirdupois †merchandise sold by weight XIV; system of weights based on the 16 oz. pound XV. ME. aver-, avoirdepeis — OF. aveir de peis ‘goods of weight’, i.e. aveir, avoir (whence ME. aver) possession (:- L. habēre have), de of, peis weight (see POISE). du for de XVII.