Definition of "mesne"

Thus all the land in the kingdom is supposed to be holden, mediately or immediately, of the sovereign, who is styled the lord paramount, or above all. Such tenants as held under the crown immediately, when they granted out portions of their lands to inferior persons, became also lords with respect to those inferior persons, as they were still tenants with respect to the king; and, thus partaking of a middle nature, were called mesne, or middle, lords. So that if the king granted a manor to A., and he granted a portion of the land to B., now B. was said to hold of A., and A. of the king ... A. was both tenant and lord, or was a mesne lord : and B. was called tenant paravail, or the lowest tenant; being he who was supposed to make avail or profit of the land.

1767, William Blackstone, “The Rights of Things”, in Commentaries on the Laws of England, volume 2, page 60

Lord, mesne, and tenant; the tenant holdeth by four pence, and the mesne by twelve pence.

1628, Sir Edward Coke, Sir Thomas Littleton, Francis Hargrave, Charles Butler, Sir Matthew Hale, Heneage Finch Earl of Nottingham, The First Part of the Institutes of the Laws of England, Or, A Commentary Upon Littleton, 16th edition, volume 1, L. Hansard & Sons,, published 1809, page 20