The Collaborative International Dictionary of English v.0.48:

Laboratory \Lab"o*ra*to*ry\, n.; pl. Laboratories. [Shortened
   fr. elaboratory; cf. OF. elaboratoire, F. laboratoire. See
   Elaborate, Labor.] [Formerly written also elaboratory.]
   1. The workroom of a chemist; also, a place devoted to
      experiments in any branch of natural science; as, a
      chemical, physical, or biological laboratory. Hence, by
      extension, a place where something is prepared, or some
      operation is performed; as, the liver is the laboratory of
      the bile.
      [1913 Webster]

   2. Hence: Any place, activity or situation suggestive of a
      scientific laboratory[1], especially in being conducive to
      learning new facts by experimentation or by systematic
      observation; as, the states serve as laboratories where
      different new policies may be tested prior to adoption
      throughout the country.
      [PJC]

WordNet (r) 3.0 (2006):

laboratory
    n 1: a workplace for the conduct of scientific research [syn:
         lab, laboratory, research lab, research laboratory,
         science lab, science laboratory]
    2: a region resembling a laboratory inasmuch as it offers
       opportunities for observation and practice and
       experimentation; "the new nation is a testing ground for
       socioeconomic theories"; "Pakistan is a laboratory for
       studying the use of American troops to combat terrorism"
       [syn: testing ground, laboratory]