The Collaborative International Dictionary of English v.0.48:

Installation \In`stal*la"tion\, n. [F. installation, LL.
   installatio: cf. It. installazione. See Install.]
   [1913 Webster]
   1. The act of installing; as, the installation of the air
      conditioner took half an hour.

   Syn: installing, setting up.
        [1913 Webster +PJC]

   2. Hence: the act of installing (a person) or giving
      possession of an office, rank, or order, with the usual
      rites or ceremonies; as, the installation of an ordained
      minister in a parish.
      [1913 Webster]

            On the election, the bishop gives a mandate for his
            installation.                         --Ayliffe.
      [1913 Webster]

   3. (Mech.) The whole of a system of machines, apparatus, and
      accessories, sometimes including the buildings and
      gorounds on which they are located, when set up and
      arranged for practical working, as in electric lighting,
      transmission of power, etc.; as, our installation in Baton
      Rouge can produce ten thousand gallons a day; we should
      move our drying installation from building A to building
      B.
      [1913 Webster +PJC]

   4. (Mil.) The whole of a military base, post, camp, outpost,
      etc., constructed and operated for support of military
      operations.
      [PJC]

WordNet (r) 3.0 (2006):

installation
    n 1: the act of installing something (as equipment); "the
         telephone installation took only a few minutes" [syn:
         installation, installing, installment, instalment]
    2: a building or place that provides a particular service or is
       used for a particular industry; "the assembly plant is an
       enormous facility" [syn: facility, installation]
    3: a formal entry into an organization or position or office;
       "his initiation into the club"; "he was ordered to report for
       induction into the army"; "he gave a speech as part of his
       installation into the hall of fame" [syn: initiation,
       induction, installation]

Moby Thesaurus II by Grady Ward, 1.0:

145 Moby Thesaurus words for "installation":
   accedence, acceptance, accession, accouterments, admission,
   admittance, agency, anchorage, apostolic orders, apparatus,
   appliances, appointment, appointments, appurtenances, armament,
   atelier, baptism, barbershop, base, beauty parlor, beauty shop,
   bench, butcher shop, calling, camp, canonization, colonization,
   coming out, company, concern, conferment, connection, consecration,
   constitution, conveniences, coronation, corporation, crowning,
   curtain raiser, debut, depot, desk, duffel, effectuation, election,
   embarkation, embarkment, enlistment, enrollment, enthronement,
   equipage, equipment, establishment, facilities, facility, firm,
   first appearance, fitting, fittings, fixation, fixtures, floating,
   flotation, formation, foundation, furnishings, furniture, gear,
   holy orders, house, immission, impedimenta, inaugural,
   inaugural address, inauguration, inception, induction, initiation,
   installations, installment, instatement, institution, introduction,
   intromission, investiture, kit, launching, lodgment, loft,
   machinery, maiden speech, major orders, materialization, materiel,
   minor orders, mooring, munition, munitions, nomination, opener,
   ordainment, orders, ordination, organization, outfit,
   paraphernalia, parlor, peopling, placement, plant, plantation,
   plumbing, population, positioning, post, preferment, preliminary,
   presentation, reading in, realization, rig, rigging, setting-up,
   settlement, settling, shop, solemnization, station, stock-in-trade,
   studio, sweatshop, tackle, taking office, things, unveiling,
   utensils, work site, work space, workbench, workhouse,
   working space, workplace, workroom, workshop, worktable



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

INSTALLATION or INSTALMENT. The act by which an officer is put in public
possession of the place he is to fill. The president of the United States,
or a governor, is installed into office, by being sworn agreeably to the
requisition of the constitution and laws. Vide Inauguration.