Cahoot (noun)

1. A secret agreement or cooperation for an illegal or deceitful purpose.
2. A partnership or collaboration, especially one that is secret or illegal.

Origin:

From french cahute, from old french cahute ("a hut"), from vulgar latin *caputia, from latin caput ("hea.d")

Examples:

1. They were in cahoots with the company to defraud investors.
2. He suspected that they were in cahoots to cheat him out of his money.
3. They were accused of being in cahoots with the enemy.
4. The two politicians were in cahoots to push their own agendas.
5. They were in cahoots, working together to deceive others.