countersue
verbEtymology From counter- + sue.
1
Law To sue a person or entity who is suing one.
- Forrest later attacked Willis in New York, knocking him to the ground; lawsuits proliferated as Willis sued Forrest for assault, and Forrest countersued for libel.2014, Eric L. Haralson, Encyclopedia of American Poetry: The Nineteenth Century, page 497: