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]