Ante-diluvian is a term used to describe something that is very old or ancient. Some antonyms for ante-diluvian could be modern, contemporary, or current. These words describe something that is new, current or up-to-date. Another antonym for ante-diluvian could be futuristic, which would describe something that is ahead of its time. The words advanced, innovative or progressive could also be used as antonyms, all of which imply the opposite of being old-fashioned or outdated. In summary, antonyms for ante-diluvian describe themes such as modernity, futurism, and innovation.