cartel

noun5

1. •
   A group of businesses or nations that collude to limit competition within an industry or market.
2. •
   (historical) A combination of political groups (notably parties) for common action.
3. •
   (historical) An official agreement concerning the exchange of prisoners.

   • He then sent down a flag of truce in military style, proposing a cartel or exchange of prisoners – the corporal for the notary. — 1832
4. •
   (historical) A written letter of defiance or challenge.

   • He is cowed at the very idea of a cartel. — 1819
5. •
   (historical) A ship used to negotiate with an enemy in time of war, and to exchange prisoners.