recoupment

2a : a keeping back of all or part of a sum sought by a plaintiff in the interest of equity — see also equitable recoupment

b : a reduction in damages because of a demand by the defendant arising out of the same occurrence or transaction

c : the right of a defendant to have the claim of the plaintiff reduced or eliminated by reason of a breach of contract or duty by the plaintiff in the same occurrence or transaction also : an affirmative defense alleging such a breach

d : a counterclaim that arises out of the same occurrence or transaction as that of the original action — compare set-off

Note: Recoupment involves the type of claim that now must be asserted in a compulsory counterclaim.