A countersuit is a legal action taken in response to an initial lawsuit filed against someone. However, there are several other similar terms to describe this type of legal proceeding. One of the most common terms is a counterclaim, which refers to a legal action that a defendant files in response to a plaintiff's claim. Another similar term is a cross-claim, which is a legal action that one defendant files against another defendant in the same case. Moreover, some people use the terms counterattack or counteraction to describe the same thing. Ultimately, regardless of the terminology used, a countersuit is an essential legal tool that allows defendants to defend their rights and interests in court.