Avoirdupois \Av`oir*du*pois"\ ([a^]v`[~e]r*d[-u]*poiz"), n. & a. [OE. aver de peis, goods of weight, where peis is fr. OF. peis weight, F. poids, L. pensum. See Aver, n., and Poise, n.]

1. Goods sold by weight. [Obs.]

2. Avoirdupois weight.

3. Weight; heaviness; as, a woman of much avoirdupois. [Colloq.]

Avoirdupois weight, a system of weights by which coarser commodities are weighed, such as hay, grain, butter, sugar, tea.

Note: The standard Avoirdupois pound of the United States is equivalent to the weight of 27.7015 cubic inches of distilled water at 62[deg] Fahrenheit, the barometer being at 30 inches, and the water weighed in the air with brass weights. In this system of weights 16 drams make 1 ounce, 16 ounces 1 pound, 25 pounds 1 quarter, 4 quarters 1 hundred weight, and 20 hundred weight 1 ton. The above pound contains 7,000 grains, or 453.54 grams, so that 1 pound avoirdupois is equivalent to 1 31-144 pounds troy. (See Troy weight.) Formerly, a hundred weight was reckoned at 112 pounds, the ton being 2,240 pounds (sometimes called a long ton).

Source: Webster's Revised Unabridged Dictionary (1913)