The Collaborative International Dictionary of English v.0.48:

Commerce \Com"merce\, n.

   Note: (Formerly accented on the second syllable.) [F.
         commerce, L. commercium; com- + merx, mercis,
         merchandise. See Merchant.]
   1. The exchange or buying and selling of commodities; esp.
      the exchange of merchandise, on a large scale, between
      different places or communities; extended trade or
      traffic.
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            The public becomes powerful in proportion to the
            opulence and extensive commerce of private men.
                                                  --Hume.
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   2. Social intercourse; the dealings of one person or class in
      society with another; familiarity.
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            Fifteen years of thought, observation, and commerce
            with the world had made him [Bunyan] wiser.
                                                  --Macaulay.
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   3. Sexual intercourse. --W. Montagu.
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   4. A round game at cards, in which the cards are subject to
      exchange, barter, or trade. --Hoyle.
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   Chamber of commerce. See Chamber.

   Syn: Trade; traffic; dealings; intercourse; interchange;
        communion; communication.
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The Collaborative International Dictionary of English v.0.48:

Chamber \Cham"ber\, n. [F. chambre, fr. L. camera vault, arched
   roof, in LL. chamber, fr. Gr. ? anything with a vaulted roof
   or arched covering; cf. Skr. kmar to be crooked. Cf.
   Camber, Camera, Comrade.]
   [1913 Webster]
   1. A retired room, esp. an upper room used for sleeping; a
      bedroom; as, the house had four chambers.
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   2. pl. Apartments in a lodging house. "A bachelor's life in
      chambers." --Thackeray.
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   3. A hall, as where a king gives audience, or a deliberative
      body or assembly meets; as, presence chamber; senate
      chamber.
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   4. A legislative or judicial body; an assembly; a society or
      association; as, the Chamber of Deputies; the Chamber of
      Commerce.
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   5. A compartment or cell; an inclosed space or cavity; as,
      the chamber of a canal lock; the chamber of a furnace; the
      chamber of the eye.
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   6. pl. (Law.) A room or rooms where a lawyer transacts
      business; a room or rooms where a judge transacts such
      official business as may be done out of court.
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   7. A chamber pot. [Colloq.]
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   8. (Mil.)
      (a) That part of the bore of a piece of ordnance which
          holds the charge, esp. when of different diameter from
          the rest of the bore; -- formerly, in guns, made
          smaller than the bore, but now larger, esp. in
          breech-loading guns.
      (b) A cavity in a mine, usually of a cubical form, to
          contain the powder.
      (c) A short piece of ordnance or cannon, which stood on
          its breech, without any carriage, formerly used
          chiefly for rejoicings and theatrical cannonades.
          [1913 Webster]

   Air chamber. See Air chamber, in the Vocabulary.

   Chamber of commerce, a board or association to protect the
      interests of commerce, chosen from among the merchants and
      traders of a city.

   Chamber council, a secret council. --Shak.

   Chamber counsel or Chamber counselor, a counselor who
      gives his opinion in private, or at his chambers, but does
      not advocate causes in court.

   Chamber fellow, a chamber companion; a roommate; a chum.

   Chamber hangings, tapestry or hangings for a chamber.

   Chamber lye, urine. --Shak.

   Chamber music, vocal or instrumental music adapted to
      performance in a chamber or small apartment or audience
      room, instead of a theater, concert hall, or church.

   Chamber practice (Law.), the practice of counselors at law,
      who give their opinions in private, but do not appear in
      court.

   To sit at chambers, to do business in chambers, as a judge.
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WordNet (r) 3.0 (2006):

chamber of commerce
    n 1: an association of businessmen to protect and promote
         business interests

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "chamber of commerce":
   Aktiengesellschaft, aktiebolag, body corporate, business,
   business establishment, cartel, combine, commercial enterprise,
   compagnie, company, concern, conglomerate,
   conglomerate corporation, consolidating company, consortium,
   copartnership, corporate body, corporation,
   diversified corporation, enterprise, firm, holding company, house,
   industry, joint-stock association, joint-stock company,
   operating company, partnership, plunderbund, pool, public utility,
   stock company, syndicate, trade association, trust, utility