cartel

noun

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