The Collaborative International Dictionary of English v.0.48:

Conservator \Con"ser*va`tor\ (?; 277), n. [L.: cf. F.
   conservateur.]
   1. One who preserves from injury or violation; a protector; a
      preserver.
      [1913 Webster]

            The great Creator and Conservator of the world.
                                                  --Derham.
      [1913 Webster]

   2. (Law)
      (a) An officer who has charge of preserving the public
          peace, as a justice or sheriff.
      (b) One who has an official charge of preserving the
          rights and privileges of a city, corporation,
          community, or estate.
          [1913 Webster]

                The lords of the secret council were likewise
                made conservators of the peace of the two
                kingdoms.                         --Clarendon.
          [1913 Webster]

                The conservator of the estate of an idiot.
                                                  --Bouvier.
          [1913 Webster]

   Conservators of the River Thames, a board of commissioners
      instituted by Parliament to have the conservancy of the
      Thames.
      [1913 Webster]

WordNet (r) 3.0 (2006):

conservator
    n 1: the custodian of a collection (as a museum or library)
         [syn: curator, conservator]
    2: someone appointed by a court to assume responsibility for the
       interests of a minor or incompetent person

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

CONSERVATOR. A preserver, a protector.
     2. Before the institution of the office of justices of the peace in
England, the public order was maintained by officers who bore the name of
conservators of the peace. All judges, justices, sheriffs and constables,
are conservators of the peace, and are bound, ex officio, to be aiding and
assisting in preserving older.
     3. In Connecticut, this term is applied to designate a guardian who has
the care of the estate of an idiot. 5 Conn. R. 280.