Webster's Dictionary 
(1): ( n.) A privilege which one has in his lands, by royal grant or prescription, of hunting and taking wild beasts and birds of warren, to the exclusion of any other person not entering by his permission.
(2): ( n.) A piece of ground for the breeding of rabbits.
(3): ( n.) A place for keeping flash, in a river.
(4): ( n.) A place privileged, by prescription or grant the king, for keeping certain animals (as hares, conies, partridges, pheasants, etc.) called beasts and fowls of warren.
King James Dictionary 
Warren, n. See Guard, Warrant and Wary.
1. A piece of ground appropriated to the breeding and preservation of rabbits. 2. In law, a franchise or place privileged by prescription or grant from the king, for keeping beasts and fowls. The warren is the next franchise in degree to the park and a forest, which is the highest in dignity, comprehends a chase, a park and a free warren. 3. A place for keeping fish in a river.