The Collaborative International Dictionary of English v.0.48:

Cartel \Car"tel\, v. t.
   To defy or challenge. [Obs.]
   [1913 Webster]

         You shall cartel him.                    --B. Jonson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cartel \Car*tel"\, n. [F., fr. LL. cartellus a little paper,
   dim. fr. L. charta. See 1st Card.]
   [1913 Webster]
   1. (Mil.) An agreement between belligerents for the exchange
      of prisoners. --Wilhelm.
      [1913 Webster]

   2. A letter of defiance or challenge; a challenge to single
      combat. [Obs.]
      [1913 Webster]

            He is cowed at the very idea of a cartel., --Sir W.
                                                  Scott.
      [1913 Webster]

   Cartel, or Cartel ship, a ship employed in the exchange
      of prisoners, or in carrying propositions to an enemy; a
      ship beating a flag of truce and privileged from capture.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cartel
    n 1: a consortium of independent organizations formed to limit
         competition by controlling the production and distribution
         of a product or service; "they set up the trust in the hope
         of gaining a monopoly" [syn: trust, corporate trust,
         combine, cartel]

Moby Thesaurus II by Grady Ward, 1.0:

145 Moby Thesaurus words for "cartel":
   Aktiengesellschaft, Anschluss, NATO, SEATO, accord, addition,
   affiliation, agglomeration, aggregation, agreement, aktiebolag,
   alliance, amalgamation, arrangement, assimilation, association,
   bargain, binding agreement, blend, blending, blow, body corporate,
   bond, business, business establishment, cabal, capitulation,
   centralization, chain, challenge, chamber of commerce, coalescence,
   coalition, collective agreement, combination, combine, combo,
   commercial enterprise, compact, compagnie, company, composition,
   concern, concord, concordat, confederacy, confederation, congeries,
   conglomerate, conglomerate corporation, conglomeration,
   conjugation, conjunction, consolidating company, consolidation,
   consortium, conspiracy, contract, convention, copartnership,
   corporate body, corporation, covenant, covenant of salt, dare,
   deal, defi, defy, dicker, diversified corporation, ecumenism,
   embodiment, employment contract, encompassment, enosis, entente,
   entente cordiale, enterprise, federalization, federation, firm,
   formal agreement, fusion, gage, gauntlet, glove, group,
   holding company, hookup, house, inclusion, incorporation, industry,
   integration, international agreement, ironclad agreement,
   joint-stock association, joint-stock company, junction, junta,
   league, legal agreement, legal contract, marriage, meld, melding,
   merger, multinational, mutual agreement, mutual-defense treaty,
   nonaggression pact, operating company, package, package deal, pact,
   paction, partnership, plunderbund, pool, promise, protocol,
   public utility, slap, solidification, stipulation, stock company,
   stump, syncretism, syndicate, syndication, syneresis, synthesis,
   tie-up, trade association, transaction, treaty, trust,
   understanding, unification, union, union contract, utility,
   valid contract, wage contract, wedding



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

CARTEL,war. An agreement between two belligerent powers for the delivery of
prisoners or deserters, and also a written challenge to a duel.
     2. Cartel ship, is a ship commissioned in time of war, to exchange
prisoners, or to carry any proposals between hostile powers; she must carry
no cargo, ammunitions, or implements of war, except a single gun for
signals. The conduct of ships of this description cannot be too narrowly
watched. The service on which they are sent is so highly important to the
interests of humanity, that it is peculiarly incumbent on all parties to
take care that it should be conducted in such a manner as not to become a
subject of jealousy and distrust between the two nations. 4 Rob. R. 357.
Vide Merl. Rep. b. t.; Dane's Ab. c. 40, a. 6, 7; Pet. C. C. R. 106; 3 C.
Rob. 141 C. Rob. 336; 1 Dods. R. 60.