A more thorough explanation:

Definition: The two-dismissal rule is a legal principle that states that when a plaintiff voluntarily dismisses a claim in one court and then files the same claim in another court, a subsequent voluntary dismissal of the same claim in the second court will be considered an adjudication on the merits, rather than a dismissal without prejudice.

Example: Let's say that a plaintiff files a lawsuit against a defendant in a state court and then voluntarily dismisses the case without prejudice. The plaintiff then files the same lawsuit against the same defendant in a federal court. If the plaintiff voluntarily dismisses the case again, the two-dismissal rule would apply, and the dismissal would be considered an adjudication on the merits.

Explanation: The two-dismissal rule is designed to prevent plaintiffs from repeatedly filing and dismissing the same claim in different courts, which can waste judicial resources and cause unnecessary delays. By treating a second voluntary dismissal as an adjudication on the merits, the rule encourages plaintiffs to carefully consider their claims before filing a lawsuit and discourages them from engaging in forum shopping.