in ancient customs, a liberty of winter-pasturage. In the counties of Norfolk and Suffolk, the lord of the manor has shack, that is, a liberty of feeding his sheep at pleasure in his tenants' lands during the six winter months.

In Norfolk, shack also extends to the common for hogs, in Shadwell, all men's grounds, from the end of harvest till seed-time. Hence to go a-shack is to feed at large.