a system of measuring weight, used in many English-speaking countries, involving a pound consisting of 16 ounces, as opposed to the metric system that uses grams and kilograms;
e.g. In the United States, most of the food you buy will be sold by avoirdupois weight, although it may also list the metric weight.
(noun)
(humorous) the heaviness or weight of a person's body;
e.g. He had put on avoirdupois since I'd last seen him, and I didn't recognize him at first.