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]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "laboratory":
   X ray, blood bank, charity ward, clinic, consultation room,
   delivery room, dispensary, emergency, examining room, fever ward,
   hospital room, intensive care, isolation, lab, labor room,
   maternity ward, nursery, operating room, pharmacy, prison ward,
   private room, proving ground, recovery room,
   research establishment, research installation, research laboratory,
   semi-private room, surgery, therapy, think tank, treatment room,
   ward