What is Serjeanty?

Legal Definition
Under feudalism in England during the mediaeval era, tenure by serjeanty was a form of tenure in return for some specified non-standard service, thus distinguishing it from knight-service. It is also used of similar forms in Continental Europe.
-- Wikipedia
Legal Definition
Eng. law. A species of service which cannot be due or performed from a tenant to any lord but the king; and is either grand or petit serjeanty.
-- Bouviers Law Dictionary
Legal Definition
A spectes of tenure by knight service, which was due to the king only, and was distinguished into grand and petit serjeanty. The tenant holding by grand serjeanty was bound, instead of attending the king generally in his wars, to do some honorary service to the king in person, as to carry his banner or sword or .to be his butler, champion or other officer at his coronation. Petit serjeanty differed from grand serjeanty, in that the service rendered to the king was not of a personui nature, but consisted in rendering him annually some small implement of war, as a bow, sword, arrow, lance or the like. Cowell; Brown.
-- Black's Law Dictionary
Legal Definition
-- Ballentine's Law Dictionary