The Collaborative International Dictionary of English v.0.48:

Conservatory \Con*serv"a*to*ry\, a. [Cf. F. conservatoire, LL.
   conservatorius.]
   Having the quality of preserving from loss, decay, or injury.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Conservatory \Con*serv"a*to*ry\, n. [Cf. F. conservatoire, LL.
   conservatorium.]
   1. That which preserves from injury. [Obs.] "A conservatory
      of life." --Jer. Taylor.
      [1913 Webster]

   2. A place for preserving anything from loss, decay, waste,
      or injury; particulary, a greenhouse for preserving exotic
      or tender plants.
      [1913 Webster]

   3. A public place of instruction, designed to preserve and
      perfect the knowledge of some branch of science or art,
      esp. music.
      [1913 Webster]

WordNet (r) 3.0 (2006):

conservatory
    n 1: the faculty and students of a school specializing in one of
         the fine arts
    2: a schoolhouse with special facilities for fine arts [syn:
       conservatory, conservatoire]
    3: a greenhouse in which plants are arranged in a pleasing
       manner [syn: conservatory, hothouse, indoor garden]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "conservatory":
   academy of music, acting school, alcove, arbor, archives, armory,
   arsenal, art school, attic, bank, basement, bay, bin,
   bonded warehouse, bookcase, bower, box, bunker, buttery,
   cargo dock, cellar, chest, choir school, cloche, closet,
   cold frame, college of architecture, coolhouse, crate, crib,
   cupboard, dancing school, depository, depot, dock, drawer, dump,
   exchequer, forcing bed, forcing house, forcing pit, gazebo,
   glasshouse, glory hole, godown, greenhouse, hold, hotbed, hothouse,
   hutch, kiosk, lathhouse, library, locker, lumber room, lumberyard,
   magasin, magazine, music school, nursery, orangery, pergola,
   pinery, rack, repertory, repository, reservoir, retreat, rick,
   salle de danse, schola cantorum, school of art, school of design,
   school of drama, seedbed, shelf, singing school, stack, stack room,
   stock room, storage, store, storehouse, storeroom, summerhouse,
   supply base, supply depot, tank, treasure house, treasure room,
   treasury, vat, vault, warehouse, wine cellar