ANCIENT DEMESNE, Eng. law. Those lands which either were reserved to the crown at the original distribution of landed property, or such as came to it afterwards, by forfeiture or other means. 1. Sal. 57; hob. 88; 4 Inst. 264; 1 Bl. Com. 286; Bac. Ab. h. t.; F. N. B. 14.