What is Collusion?

Legal Definition
Collusion is an agreement between two or more parties, sometimes illegal and therefore secretive, to limit open competition by deceiving, misleading, or defrauding others of their legal rights, or to obtain an objective forbidden by law typically by defrauding or gaining an unfair market advantage. It is an agreement among firms or individuals to divide a market, set prices, limit production or limit opportunities. It can involve "wage fixing, kickbacks, or misrepresenting the independence of the relationship between the colluding parties". In legal terms, all acts effected by collusion are considered void.
-- Wikipedia
Legal Definition
A collaborative agreement, usually secret, amongst rivals to prevent open competition through deceptive means in order to gain a market advantage. The parties may collude by agreeing to fix prices, limit or restrict supply, share insider information, or divide the market.
Legal Definition
Fraud. An agreement between two or more persons, to defraud a person of his rights by the forms of law, or to obtain an object forbidden by law; as, for example, where the husband and wife collude to obtain a divorce for a cause not authorized by law. It is nearly synonymous with covin. (q. v.)

2. Collusion and fraud of every kind vitiate all acts which are infected with them, and render them void. Vide Shelf. on Mar. .& Div. 416, 450; 3 Hagg. Eccl. R. 130, 133; 2 Greenl. Ev. 51; Bousq. Dict. de Dr. mot Abordage.
-- Bouviers Law Dictionary
Legal Definition
A deceitful agreement or compact between two or more persons, for the one party to bring an action against the other for some evil purpose, as to defraud a third party of his right. Cowell.

A secret arrangement between two or more persons, whose interests are apparently conflicting, to make use of the forms and proceedings of law in order to defraud a third person, or to obtain that which justice would not give them, by deceiving a court or it officers. Baldwin v. New York, 45 Barb. (N. Y.) 359; Belt v. Blackburn, 28 Md. 235; Railroad Co. v. Gay, 86 Tex. 571, 26 S. W. 599, 25 In In A. 52; Balch v. Beach, 119 Wis. 77, 95 N. W. 132.

In divorce proceedings; collusion is an agreement between husband and wife that one of them shall commit, or appear to have committed, or be represented in court as having committed, acts constituting a cause of divorce, for the purpose of enabling the other to obtain a divorce. Civil Code Cal. ยง 114. But it also means connivance or conspiracy in initiating or prosecuting the suit, as where there is a compact for mutual aid in carrying it through to a decree. Beard v. Beard, 65 CaL 354, 4 Pac. 229; Pohlman v. Pohiman, 60 N. J. Eq. 28, 46 Atl. 658; Drayton v. Drayton. 54 N. J. Eq. 298, 38 Atl. 25.
-- Black's Law Dictionary
Legal Definition
An agreement to defraud a third party of his rights by the forms of law, or to secure an unlawful object. See 157 N. Y. 259, 68 Am. St. Rep. 777, 43 L. R. A. 256, 51 N. E. 1036.
-- Ballentine's Law Dictionary