What it means
A counterclaim is a claim made by a defendant against the plaintiff within the same proceeding, rather than in a separate case. It is typically filed together with the defence and is decided at the same time. For example, a defendant sued for an unpaid invoice might counterclaim for the cost of fixing defective work. A related claim against another party is often called a cross-claim.
How it's used
The builder filed a defence and a counterclaim seeking payment for extra work she had carried out.