Talāq al bāin means an irrevocable divorce in Islamic law. It is a type of divorce that is final and cannot be undone or revoked. Once the husband pronounces the talāq al bāin, the marriage is terminated, and the couple cannot reconcile without the wife marrying another man and then getting divorced from him. This type of divorce is considered a last resort in Islam and is discouraged unless there are valid reasons for it.