NOUN (3)

1. (economics) a market in which there are many buyers but only one seller;
- Example: "a monopoly on silver"
- Example: "when you have a monopoly you can ask any price you like"

2. exclusive control or possession of something;
- Example: "They have no monopoly on intelligence"

3. a board game in which players try to gain a monopoly on real estate as pieces advance around the board according to the throw of a die;

The Collaborative International Dictionary of English v.0.48:

Monopoly \Mo*nop"o*ly\, n.; pl. Monopolies. [L. monopolium,
   Gr. ?, ?; mo`nos alone + ? to sell.]
   1. The exclusive power, or privilege of selling a commodity;
      the exclusive power, right, or privilege of dealing in
      some article, or of trading in some market; sole command
      of the traffic in anything, however obtained; as, the
      proprietor of a patented article is given a monopoly of
      its sale for a limited time; chartered trading companies
      have sometimes had a monopoly of trade with remote
      regions; a combination of traders may get a monopoly of a
      particular product.
      [1913 Webster]

            Raleigh held a monopoly of cards, Essex a monopoly
            of sweet wines.                       --Macaulay.
      [1913 Webster]

   2. Exclusive possession; as, a monopoly of land.
      [1913 Webster]

            If I had a monopoly out, they would have part on 't.
                                                  --Shak.
      [1913 Webster]

   3. The commodity or other material thing to which the
      monopoly relates; as, tobacco is a monopoly in France.
      [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

monopoly
    n 1: (economics) a market in which there are many buyers but
         only one seller; "a monopoly on silver"; "when you have a
         monopoly you can ask any price you like"
    2: exclusive control or possession of something; "They have no
       monopoly on intelligence"
    3: a board game in which players try to gain a monopoly on real
       estate as pieces advance around the board according to the
       throw of a die

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "monopoly":
   a corner on, arrest, arrestation, bear raid, bull raid, cartel,
   check, consortium, constraint, control, cooling, cooling down,
   cooling off, copyright, corner, corner in, cornering, curb,
   curtailment, deceleration, engrossment, exclusive possession,
   forestallment, hindrance, inhibition, injunction, interdict,
   legal restraint, manipulation, monopolization, ownership, pool,
   possessorship, prohibition, proprietorship, protection,
   protectionism, protective tariff, raid, rationing, rein, restraint,
   restraint of trade, retardation, retrenchment, rigging,
   self-control, slowing down, syndicate, tariff wall,
   thought control, trust, wash sale, washing



Bouvier's Law Dictionary, Revised 6th Ed (1856):

MONOPOLY, commercial law. This word has various significations. 1. It is the
abuse of free commerce by which one or more individuals have procured the
advantage of selling alone all of a particular kind of merchandise, to the
detriment of the public.
     2.-2. All combinations among merchants to raise the price of
merchandise to the injury of the public, is also said to be a monopoly.
     3.-3. A monopoly is also an institution or allowance by a grant from
the sovereign power of a state, by commission, letters patent, or otherwise,
to any person, or corporation, by which the exclusive right of buying,
selling, making, working, or using anything, is given. Bac. Abr. h.t.; 3
Inst. 181.
     4. The constitutions of Maryland, North Carolina, and Tennessee,
declare that "monopolies are contrary to the genius of a free government,
and ought not to be allowed." Vide art. Copyright; Patent.