If you are sued for breaching a contract and you, in turn, also file suit against the plaintiff and claim thathe was really the one who breached the contract, your claim against the original plaintiff is an example of a counterclaim.
intransitive verbcoun·ter·claimed, coun·ter·claim·ing, coun·ter·claims
(third-person singular simple present counterclaims, present participle counterclaiming, simple past and past participle counterclaimed)
- (intransitive) To file a counterclaim.
counterclaim - Legal Definition