(biblical) A person who lived in the time prior to the great flood described in Genesis, especially one of the biblical patriarchs.

(figurative, hyperbolic, chiefly humorous) A noun "antediluvian" represents a very old person or a person with extremely old-fashioned attitudes.

(biblical) Belonging or pertaining to, or existing in, the time prior to the great flood described in Genesis, or to a great or destructive flood or deluge described in other mythologies.

(by extension) Of animals and plants: long extinct; prehistoric.

(figurative, hyperbolic, chiefly humorous) An adjective "antediluvian" describes something or someone as very old or ancient, and also refers to attitudes or ideas that are extremely old-fashioned or antiquated.