Legal Definition of Intervention: An act wherein a third person seeks to become a party to a suit between two other persons. He may wish to join the plaintiff in pressing a suit against a defendant or he may wish to join the defendant against the plaintiff | Learn the legal definition of intervention and how it can impact your business. Discover examples of intervention and understand why it is crucial in various legal proceedings. Safeguard your rights and interests by actively participating in lawsuits. Seek professional legal advice for complex matters