noun /ˌævədəˈpɔɪz,ˌævɑːdjuːˈpwɑː,ˌævɚdəˈpɔɪz/
a) The official system of weights used in UK between 1856 and 1963. It had been the customary system in London since 1300 .
he has a lot of avoirdupois
b) The official system of weights used in USA between 1866 and 1959.
Wikipedia foundation.