confession and avoidance

Definition from Nolo’s Plain-English Law Dictionary

A plea, or answer, to a complaint in a civil case, in which the defendant admits the allegations in the lawsuit but alleges other facts that, if found to be true by the trier of fact, will negate the negative effect of the plaintiff's claims. For example, in a few states, a plaintiff who sues over injuries allegedly caused by the defendant's negligence will not recover any damages if the defendant can prove that the plaintiff was in part also negligent (contributory negligence). When a defendant admits having acted negligently, but alleges that the plaintiff was also careless, the defendant has entered a plea of confession and avoidance.

Definition provided by Nolo’s Plain-English Law Dictionary.