set off

noun | \ ˈset-ˌȯf \

1. : the reduction or discharge of a debt by setting against it a claim in favor of the debtor; specifically : the reduction or discharge of a party's debt or claim by an assertion of another claim arising out of another transaction or cause of action against the other party : the reduction or discharge of a party's debt or claim by an assertion of another claim arising out of another transaction or cause of action against the other party

2. a : a right to seek reduction or discharge of a debt or claim by countering a party's claim with an independent claim

   b : a counterclaim made by a defendant against a plaintiff for reduction or discharge of a debt by reason of an independent debt owed by the plaintiff to the defendant — compare recoupment 2

transitive verb

1. : to reduce or discharge by set-off : offset