counterclaim

noun

1. A suit filed by a defendant against a plaintiff secondary to the original complaint.
2. A claim (assertion) that counters (disputes) another.

   “Develop claims and counterclaims fairly and thoroughly, supplying the most relevant data and evidence for each while pointing out the strengths and limitations of both claims and counterclaims in a discipline-appropriate form that anticipates the audience's knowledge level, concerns, values, and possible biases.”

verb

1. (intransitive)To file a counterclaim.