Dictionary.net

This is a French phrase, which signifies without number.

In England it is used in relation to the right of putting animals on a common. The term common sans nombre does not mean that the beasts are to be innumerable, but only indefinite, not certain; Willes, 227; but they are limited to the commoner's own commonable cattle, levant et couchant, upon his lands, or as many cattle as the land of the commoner can keep and maintain in winter. 2 Brownl. 101; Vent. 54; 5 T. R. 48; 1 Saund. 28, n. 4.