The Collaborative International Dictionary of English v.0.48:

Mandate \Man"date\, n. [L. mandatum, fr. mandare to commit to
   one's charge, order, orig., to put into one's hand; manus
   hand + dare to give: cf. F. mandat. See Manual, Date a
   time, and cf. Commend, Maundy Thursday.]
   1. An official or authoritative command, order, or
      authorization from a superior official to a subordinate;
      an order or injunction; a commission; a judicial precept.
      [1913 Webster]

            This dream all-powerful Juno; I bear
            Her mighty mandates, and her words you hear.
                                                  --Dryden.
      [1913 Webster]

   2. Hence: (Politics) An authorization to carry out a specific
      public policy, given by the electorate to their
      representatives; -- it is considered to be implied by the
      election of a candidate by a significant margin after that
      candidate has campaigned with that policy as a prominent
      element of the campaign platform.
      [PJC]

   3. Hence: Authorization by a multinational body to a nation
      to administer the government and affairs of a territory,
      usually a former colony; as, termination of the British
      mandate in Palestine.
      [PJC]

   4. (Canon Law) A rescript of the pope, commanding an ordinary
      collator to put the person therein named in possession of
      the first vacant benefice in his collation.
      [1913 Webster]

   5. (Scots Law) A contract by which one employs another to
      manage any business for him. By the Roman law, it must
      have been gratuitous. --Erskine.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

219 Moby Thesaurus words for "mandate":
   adverse possession, agency, agentship, ally, alodium, archduchy,
   archdukedom, assignment, authority, authorization, behest,
   bench warrant, bid, bidding, body politic, brevet, buffer state,
   burgage, call on, call the signals, call upon, capias,
   captive nation, care, caveat, charge, chieftaincy, chieftainry,
   city-state, claim, colony, command, commission, commissioning,
   commitment, commonweal, commonwealth, consignment,
   constitutional referendum, country, county, cure, de facto,
   de jure, death warrant, declare, decree, delegated authority,
   delegation, dependency, deputation, derivative title, devolution,
   devolvement, dictate, direct, direct initiative, domain, dominion,
   duchy, dukedom, earldom, embassy, empery, empire, empowerment,
   enjoin, entrusting, entrustment, errand, executorship, exequatur,
   factorship, facultative referendum, fee fief, fee position,
   fee simple, fee simple absolute, fee simple conditional,
   fee simple defeasible, fee simple determinable, fee tail, feodum,
   feud, fiat, fiefdom, fieri facias, frankalmoign, free city,
   free socage, freehold, full power, gavelkind, give an order,
   give the word, grand duchy, habere facias possessionem,
   having title to, hold, holding, imperative, indirect initiative,
   initiative, injunction, instruct, interdict, issue a command,
   issue a writ, jurisdiction, kingdom, knight service, land, lay fee,
   lease, leasehold, legal claim, legal possession, legation, license,
   lieutenancy, mandamus, mandant, mandated territory, mandatee,
   mandatory, mandatory injunction, mandatory referendum, mission,
   mittimus, nation, nationality, nisi prius, notice, notification,
   occupancy, occupation, office, ordain, order, order about,
   original title, owning, plebiscite, plebiscitum,
   plenipotentiary power, polis, polity, possessing, possession,
   power, power of attorney, power to act, precept, preoccupancy,
   preoccupation, prepossession, prescription, principality,
   principate, process, proclaim, procuration, prohibitory injunction,
   promulgate, pronounce, property, property rights,
   proprietary rights, protectorate, province, proxy,
   puppet government, puppet regime, purview, realm, recall,
   referendum, regency, regentship, republic, responsibility, rule,
   satellite, say the word, search warrant, seisin, seneschalty,
   settlement, socage, sovereign nation, squatting, state,
   statutory referendum, sublease, sultanate, superpower, task,
   tenancy, tenantry, tenure, tenure in chivalry, territory, title,
   toparchia, toparchy, trust, trusteeship, underlease, undertenancy,
   usucapion, vicarious authority, villein socage, villeinhold,
   villenage, warrant, warrant of arrest, warrant of attorney, word,
   writ