noun

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