In law, an action that is instituted maliciously and without probable cause: A vexatious proceeding is a type of malicious prosecution based on a civil procedure that exists when the party bringing the transaction is not sincere and is merely trying to annoy or to embarrass his opponent or when it is not calculated to lead to any practical result.

A vexatious proceeding is often described as frivolous and not worthy of serious consideration; so, the court may dismiss it on that ground.