A cause of action or claim for relief asserted in opposition to or as a setoff against the plaintiff's own cause of action or claim for relief and contained in the defendant's answer to the plaintiff's complaint. See also crossclaim. compulsory counterclaim. A cause of action or claim for relief that arises from the same occurrence, transaction, or subject matter as the plaintiff's cause of action or claim for relief. Generally, the failure to raise such cause of action or claim for relief in...