The number of grazing animals, especially cows or sheep, that can be sustained on an area of pasture. Also in "a soum of sheep": a definite quantity of sheep, defined as the number that can be sustained on a certain amount of pasture, and varying in different places from four to ten. Now chiefly historical.

The amount of grazing land which will sustain one cow (and sometimes also her most recent calf or calves), or a proportional number of sheep or other grazing animals. Now chiefly historical.

To examine (an area of pasture) in order to determine how many grazing animals it can sustain. In later use also: to include (an animal) in a calculation to determine how much livestock an area of pasture can sustain.