1. past tense of countersue; to sue someone who has sued you
Usage: legal term; transitive verb

Examples

• After being sued for breach of contract, the company countersued for defamation.
• The defendant countersued the plaintiff for damages caused by the false allegations.
• She countersued her former employer after he filed a lawsuit against her.
• The two parties countersued each other over the disputed property rights.
• When the contractor was sued for poor workmanship, he countersued for non-payment.
• The corporation countersued its rival in response to the patent infringement claim.