What does antediluvial mean?
Antediluvial means 'before the deluge' — originally, belonging to the era prior to the great Flood described in the Book of Genesis. In the seventeenth and eighteenth centuries the term had genuine scientific currency: naturalists used it to label rocks, fossils, and landscapes they believed predated Noah's Flood. As geology matured and abandoned flood-based explanations of Earth's history, that literal sense faded, and the word settled into a figurative role. Today antediluvial is used, often with a wry or mocking tone, to describe anything astonishingly old, primitive, or out of step with the present — a bureaucratic procedure, a piece of machinery, or a set of attitudes inherited from a vanished age. It functions as a colourful, more emphatic alternative to words like archaic or antiquated. A closely related and considerably more frequent variant, antediluvian, shares both meanings; writers choosing between them should note that antediluvial is the rarer, more bookish of the two.
adjectiveOf or relating to the period before the biblical Flood; by extension, extremely old, outdated, or primitive.
- Relating to the period before the biblical Flood (the original, literal sense).
- Extremely old, antiquated, or hopelessly out of date (the common figurative sense today).
"The museum's filing system was so antediluvial that staff still recorded loans in a leather ledger."
"Critics dismissed the proposal as an antediluvial relic of nineteenth-century thinking."
"Fossil hunters in the 1700s debated whether the strange bones were antediluvial creatures drowned in Noah's Flood."
Before geologists gave us 'prehistoric', scientists literally divided Earth's history into the age before the Flood and everything after — and 'antediluvial' is what they called the before part.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of antediluvial
Antediluvial derives from Latin: the prefix ante- ('before') combined with diluvium ('flood, deluge'), the Latin term behind English 'diluvial' and cognate with 'deluge'. The word entered English in the early modern period, when scholars writing in Latin-influenced vocabulary needed a term for the pre-Flood world. Its sibling form antediluvian arose from the same elements via diluvium's adjectival derivative and ultimately became the dominant English variant. Related terms sharing the diluvium root include diluvial and alluvial, the latter from alluvius ('washed against').
Related word forms
How antediluvial is actually used
The word is formal and somewhat literary; in everyday use most writers reach for its near-twin 'antediluvian', which dominates modern usage. The figurative sense — describing anything laughably outdated — is now far more common than the literal geological or theological sense. When used figuratively it often carries a mildly humorous or mocking connotation.
Easily confused with antediluvial
Antediluvian is the far more common form of the same word; antediluvial is a rarer variant with identical meaning.
Alluvial refers to sediment deposited by flowing water, whereas antediluvial refers to the time before the biblical Flood or to anything extremely old-fashioned.