cartel

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A combination of independent business organizations formed to regulate production, pricing, and marketing of goods by the members.
• noun An official agreement between governments at war, especially one concerning the exchange of prisoners.
• noun A group of parties, factions, or nations united in a common cause; a bloc.

from The Century Dictionary.

• To defy; challenge to a duel. Also chartel.
• noun A writing or an agreement between states, especially when at war, as for the exchange of prisoners, or for some mutual advantage.
• noun A letter of defiance or challenge; a challenge to single combat.
• noun Formerly also chartel.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Mil.) An agreement between belligerents for the exchange of prisoners.
• noun obsolete A letter of defiance or challenge; a challenge to single combat.
• noun 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.
• transitive verb obsolete To defy or challenge.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A group of businesses or nations that collude to limit competition within an industry or market.
• noun A combination of political groups (notably parties) for common action
• noun A written letter of defiance or challenge.
• noun An official agreement concerning the exchange of prisoners.
• noun nautical A ship used to negotiate with an enemy in time of war, and to exchange prisoners.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a consortium of independent organizations formed to limit competition by controlling the production and distribution of a product or service