Vexatious litigation

Vexatious litigation is legal action which is brought, regardless of its merits, solely to harass or subdue an adversary. It may take the form of a primary frivolous lawsuit or may be the repetitive, burdensome, and unwarranted filing of meritless motions in a matter which is otherwise a meritorious cause of action. Filing vexatious litigation is considered an abuse of the judicial process and may bring down sanctions on the offender. Roy L. Pearson, Jr., an Administrative Law Judge in the District of Columbia, who sued a dry-cleaner for $54 million for allegedly losing a pair of his trousers, is sometimes used as an example of a vexatious litigant.
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Noun
1. litigation shown to have been instituted maliciously and without probable cause; "he got an injunction against vexatious litigation by his enemies"
(hypernym) litigation, judicial proceeding
(classification) law, jurisprudence