Source : Webster's Revised Unabridged Dictionary (1913)

Thirlage \Thirl"age\, n. [Cf. {Thrall}.] (Scots Law)
   The right which the owner of a mill possesses, by contract or
   law, to compel the tenants of a certain district, or of his
   sucken, to bring all their grain to his mill for grinding.
   --Erskine.