A secret plan to achieve an evil or illegal end
He was loudly accused by the Catholics of collusion with the enemies of the faith.
The two smugglers acted in collusion to transport the illegal goods over the border.
He was master of the holy cities, and the official Moniteur Ottoman denounced his supposed plan of aiming at the caliphate in collusion with the sherif of Mecca.
Was there collusion among the major technology corporations to suppress wages for their workers?
Everyone was wondering if there was enough evidence to point to collusion between the two leaders.