What is Copyhold?

Legal Definition
Copyhold tenure was a form of customary tenure of land common in England from the Middle Ages. The land was held according to the custom of the manor, and the mode of landholding took its name from the fact that the "title deed" received by the tenant was a copy of the relevant entry in the manorial court roll. A tenant who held land in this way was known as a copyholder.
-- Wikipedia
Legal Definition
Estate in the English law. A copyhold estate is a parcel of a manor, held at the will of the lord, according to the custom of the manor, by a grant from the lord, and admittance of the tenant, entered on the rolls of the manor court. Cruise, Dig. t. 10, c. 1, s. 3. Vide Ch. Pr. Index, h. t.
-- Bouviers Law Dictionary
Legal Definition
A species of estate at will or customary estate In England, the only visible title to which consists of the copies of the court rolls, which are made out by the steward of the manor, on a tenant's being admitted to any parcel of land or tenement belonging to the manor. It is an estate at the will of the lord, yet such a will as is agreeable to the custom of the manor, which customs are preserved and evidenced by the rolls of the several courts baron, in which they are entered. 2 Bl. Comm. 95. In a larger sense, copyhold is said to import every customary tenure, (that is, every tenure pending on the particular custom of a manor,) as opposed to fuse socage or freehold, which may now (since the abolition of knight-service) be considered as the general or common-law tenure of the country. 1 Steph. Comm. 210.
See also
-- Black's Law Dictionary
Legal Definition
An English land tenure in which the tenant held under a copy of the roll in the lord’s court; the land so held. See 2 Bl. Comm. 95.
-- Ballentine's Law Dictionary