cartel

Short definition from Wiktionary

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.