Postdiluvian is a rarely used term in modern language and is often used in biblical and historical contexts to describe the period after the biblical flood. Some synonyms for postdiluvian include "post-flood," "after the deluge," "antideluvian," "post-Noahic," and "postdiluvial." These terms are all used to describe the time after the great flood mentioned in the Bible. While some of these terms may be more commonly used in certain settings, they can all be used to describe the same period in history. Using synonyms like these can help to add variety and clarity to writing and conversation.