The Collaborative International Dictionary
Sergeanty \Ser"geant*y\, n. [Cf. OF. sergentie, LL. sergentia. See Sergeant.] (Eng. Law) Tenure of lands of the crown by an honorary kind of service not due to any lord, but to the king only. [Written also serjeanty.]
Grand sergeanty, a particular kind of tenure by which the
tenant was bound to do some special honorary service to
the king in person, as to carry his banner, his sword, or
the like.
--Tomlins.
--Cowell.
--Blackstone.
Petit sergeanty. See under Petit.
Wiktionary
n. (context British English) A form of land ownership under the feudal system, where a family held an estate in exchange for rendering a service to their liege lord.
Wikipedia
Under the feudal system in late and high medieval England, tenure by serjeanty was a form of land-holding in return for some specified service, ranking between tenure by knight-service ( enfeoffment) and tenure in socage. It is also used of similar forms in Continental Europe.
Usage examples of "serjeanty".
Jack's concern with petty serjeanty was so slight that he carried straight on, "I dare say I have been in command too long.
We will not by reason of any small serjeanty which any one may hold of us by the service of rendering to us knives, arrows, or the like, have wardship of his heir or of the land which he holds of another lord by knightâs service.