conservator

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A person in charge of maintaining or restoring valuable items, as in a museum or library.
• noun A protector or guardian.
• noun Law One placed in charge of the property or personal affairs of an incompetent person.

from The Century Dictionary.

• noun A preserver; one who or that which preserves from injury, violation, or infraction: as, a conservator of the peace. See phrases below.
• noun Specifically — , A person appointed to superintend idiots, lunatics, etc., manage their property, and preserve it from waste.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who preserves from injury or violation; a protector; a preserver.
• noun An officer who has charge of preserving the public peace, as a justice or sheriff.
• noun One who has an official charge of preserving the rights and privileges of a city, corporation, community, or estate.
• noun a board of commissioners instituted by Parliament to have the conservancy of the Thames.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who conserves, preserves or protects something.
• noun law A person appointed by a court to manage the affairs of another; similar to a guardian but with some powers of a trustee.
• noun Roman Catholicism A judge delegated by the pope to defend certain privileged classes of persons from manifest or notorious injury or violence, without recourse to a judicial process.
• noun A professional who works on the conservation and restoration of objects, particularly artistic objects.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun someone appointed by a court to assume responsibility for the interests of a minor or incompetent person
• noun the custodian of a collection (as a museum or library)