in league with

• alliedJoined in partnership
• colludingSecretly cooperating for deception
• conspiringPlotting secretly with others
• cahootsInformal term for conspiracy
• partneredJoined with another

complicit · scheming · confederate · accomplice · plotting · cohorts · syndicate · pact · secret · handshake · backroom · deal · collusion · collaborating · joined · united · sworn · bound