The Collaborative International Dictionary of English v.0.48:

Servient \Serv"i*ent\, a. [L. serviens, -entis, p. pr. See
   Serve.]
   Subordinate. [Obs. except in law.] --Dyer.
   [1913 Webster]

   Servient tenement or Servient estate (Law), that on which
      the burden of a servitude or an easement is imposed. Cf.
      Dominant estate, under Dominant. --Gale & Whately.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

SERVIENT, civil law. A term applied to an estate or tenement by which a
servitude is due to another estate or tenement. See Dominant; Servitude.