Nolo's Plain-English Law Dictionary

Vexatious Litigation

A lawsuit that is filed when there is no legal basis, and with the purpose to bother, annoy, embarrass, and cause legal expenses to the defendant. Vexatious litigation also includes continuing a lawsuit after discovery of the facts shows it has absolutely no merit. Vexatious litigation may lead to a legal claim of malicious prosecution against the vexatious litigant. Most states allow a judge to penalize plaintiffs and attorneys for filing or continuing a frivolous legal action. (See also: frivolous)
NOLO-web1:DRU1.6.8.27.20160921.41205