The Collaborative International Dictionary of English v.0.48:

Labyrinth \Lab"y*rinth\, n. [L. labyrinthus, Gr. laby`rinthos:
   cf. F. labyrinthe.]
   1. An edifice or place full of intricate passageways which
      render it difficult to find the way from the interior to
      the entrance; as, the Egyptian and Cretan labyrinths.
      [1913 Webster]

   Note: The Labyrinth of Classical Mythology was a vast maze
         constructed by Daedalus on the island of Crete, in
         order to confine the Minotaur; the task was done at the
         command of King Minos. One theory suggests that the
         myth had some basis in the structure of the palace of
         King Minos at Knossos, in Crete, it being a
         multistoried royal palace with labyrinthine passages
         between rooms.
         [PJC]

   2. Hence: Any intricate or involved inclosure; especially, an
      ornamental maze or inclosure in a park or garden, having
      high hedges separating confusingly convoluted passages.
      [1913 Webster]

   3. Any object or arrangement of an intricate or involved
      form, or having a very complicated nature.
      [1913 Webster]

            The serpent . . . fast sleeping soon he found,
            In labyrinth of many a round self-rolled. --Milton.
      [1913 Webster]

            The labyrinth of the mind.            --Tennyson.
      [1913 Webster]

   4. An inextricable or bewildering difficulty.
      [1913 Webster]

            I' the maze and winding labyrinths o' the world.
                                                  --Denham.
      [1913 Webster]

   5. (Anat.) The internal ear. See Note under Ear.
      [1913 Webster]

   6. (Metal.) A series of canals through which a stream of
      water is directed for suspending, carrying off, and
      depositing at different distances, the ground ore of a
      metal. --Ure.
      [1913 Webster]

   7. (Arch.) A pattern or design representing a maze, -- often
      inlaid in the tiled floor of a church, etc.
      [1913 Webster]

   Syn: Maze; confusion; intricacy; windings.

   Usage: Labyrinth, Maze. Labyrinth, originally; the name
          of an edifice or excavation, carries the idea of
          design, and construction in a permanent form, while
          maze is used of anything confused or confusing,
          whether fixed or shifting. Maze is less restricted in
          its figurative uses than labyrinth. We speak of the
          labyrinth of the ear, or of the mind, and of a
          labyrinth of difficulties; but of the mazes of the
          dance, the mazes of political intrigue, or of the mind
          being in a maze.
          [1913 Webster]

WordNet (r) 3.0 (2006):

labyrinth
    n 1: complex system of paths or tunnels in which it is easy to
         get lost [syn: maze, labyrinth]
    2: a complex system of interconnecting cavities; concerned with
       hearing and equilibrium [syn: inner ear, internal ear,
       labyrinth]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "labyrinth":
   Chinese puzzle, Gordian knot, Rube Goldberg contraption,
   can of worms, complex, jungle, knot, maze, meander, mesh, mess,
   morass, perplex, ravel, skein, snafu, snake pit, snarl, tangle,
   tangled skein, web, webwork, wheels within wheels, wilderness