ADJ-GRADED [usually ADJ n](尤指国家、组织间)共谋的,勾结的,串通的Collusive behaviour involves secret or illegal co-operation, especially between countries or organizations. (尤指国家、组织间)共谋的,勾结的,串通的 [formal, disapproval]
Any evidence of collusive behaviour by the banks could be sent to the Office of Fair Trading.