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 ) < Latin collūsiōn- (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).