a secret agreement, especially for fraudulent or treacherous purposes; conspiracy: Some of his employees were acting in collusion to rob him.
2.
Law.a secret understanding between two or more persons to gain something illegally, to defraud another of his or her rights, or to appear as adversaries though in agreement: collusion of husband and wife to obtain a divorce.
Origin: 1350–1400;Middle English (< Middle French) < Latincollūsiōn- (stem of collūsiō), equivalent to collūs(us) (past participle of collūdere to collude) + -iōn--ion
1389, from O.Fr. collusion, from L. collusionem "act of colluding," from colludere, from com- "together" + ludere "to play," from ludus "game" (see ludicrous).