Judicial application by which a person being sued (the defendant) introduces against the plaintiff, in the same file, conclusions resulting from the same source, in addition to the dismissal of the principal application. This is for example, the case of the syndicate of co-owners which, summoned in nullity of a decision of meeting of co-owners, seeks the condemnation of the co-owner plaintiff to the payment of damages because of the futile and vexatious nature of the main claim.