From ante- (prefix meaning ‘prior to in time’) +‎ Latin dīluvium (“a flood”) +‎ -an (suffix meaning ‘of or pertaining to’ forming adjectives; and forming agent nouns),^[1] referring the story of Noah’s Ark, through which God rescues Noah, his family, and examples of all the world’s animals from the great flood, which is related in Genesis 6–9 of the Bible. Dīluvium is derived from dīluō (“to wash away”) (from dis- (prefix meaning ‘apart, asunder, in two’) + lavō (“to wash”) (ultimately from Proto-Indo-European *lewh₃- (“to wash”))) + -ium (suffix forming abstract nouns). The English word is analysable as ante- +‎ diluvian.

Sense 2 (“long extinct”) is from the fact that such animals and plants were originally believed to have perished in the biblical flood referred to above.^[1]

• (Received Pronunciation) IPA^(key): /ˌæn.tɪ.dɪˈluː.vɪ.ən/
• (General American) IPA^(key): /ˌæn.ti.dəˈlu.vi.ən/, /-tə-/, /ˌæn.tə(ˌ)daɪˈlu.vi.ən/, [-ɾi-], [-ɾə-]

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• Rhymes: -uːviən
• Hyphenation: an‧ti‧di‧luv‧i‧an

antediluvian (comparative more antediluvian, superlative most antediluvian)

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

   Synonyms: antediluvial, prediluvian, preflood

   Coordinate term: prelapsarian

   • 1646, Thomas Browne, “Of Methuselah”, in Pseudodoxia Epidemica: […], London: […] T[homas] H[arper] for Edward Dod, […], →OCLC, 7th book, pages 343–344:

     [P]erhaps ſome perſons might outlive Methuſelah; the Text intending onely the maſculine line of Seth, conduceable unto the Genealogy of our Saviour, and the antediluvian Chronology.

   • 1727, [Daniel Defoe], “Of what Shapes the Devil Assum’d in His First Appearances to the Magicians, and Others, in the First Ages of the World; and whether He is, or has been,, Allow’d to Assume a Human Shape, or No”, in A System of Magick; or, A History of the Black Art. […], London: […] J. Roberts […], →OCLC, page 95:

     For Noah, vvho had no doubt preach'd againſt the Vices of the Antediluvian VVorld, and againſt Drunkenneſs among the reſt, muſt certainly knovv the Uſe of the Vine, and the Abuſe of it too; hovv elſe did he come to plant it at all, and to preſs the Juice out for Drinking it at all?

   • 1968 November, Donovan Leitch (lyrics and music), “Atlantis”, in Barabajagal, performed by Donovan, New York, N.Y.: Epic Records, →OCLC:

     The great Egyptian age is but a remnant of the Atlantean culture / The antediluvian kings colonized the world / All the gods who play in the mythological dramas / In all legends from all lands were from fair Atlantis

4. (by extension) Of animals and plants: long extinct; prehistoric.
   • 1851 November 14, Herman Melville, “The Fossil Whale”, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley, →OCLC, page 506:

     Having already described him [the whale] in most of his present habitatory and anatomical peculiarities, it now remains to magnify him in an archæological, fossiliferous, and antediluvian point of view.

5. (figurative, hyperbolic, chiefly humorous)
   1. Of a person or thing: very old; ancient.

      Synonyms: prehistoric; see also Thesaurus:old

      Antonyms: see Thesaurus:young

      • 1823, Elia [pseudonym; Charles Lamb], “A Dissertation upon a Roast Pig”, in Elia. Essays which have Appeared under that Signature in The London Magazine, London: […] [Thomas Davison] for Taylor and Hessey, […], →OCLC, page 277:

        [H]is eldest son Bo-bo, […] let some sparks escape into a bundle of straw, which kindling quickly, spread the conflagration over every part of their poor mansion, till it was reduced to ashes. Together with the cottage (a sorry antediluvian make-shift of a building, you may think it), what was of much more importance, a fine litter of new-farrowed pigs, no less than nine in number, perished.

      • 1969 November 10, John Fowles, chapter 12, in The French Lieutenant’s Woman, 1st US edition, Boston, Mass.; Toronto, Ont.: Little, Brown and Company […], →OCLC, page 90:

        There was an antediluvian tradition (much older than Shakespeare) that on Midsummer's Night young people should go with lanterns, and a fiddler, and a keg or two of cider, to a patch of turf known as Donkey's Green in the heart of the woods and there celebrate the solstice with dancing.

      • 2003, Dan Brown, chapter 54, in The Da Vinci Code, [London]: BCA, published 2005, page 226:

        The air inside smelled antediluvian, regal somehow, with traces of pipe tobacco, tea leaves, cooking sherry, and the earthen aroma of stone architecture.

      • 2010, Sam Chaltain, “Connect (or, Make the Connections that Let You ‘See the Whole Board’)”, in American Schools: The Art of Creating a Democratic Learning Community, Lanham, Md.: Rowman & Littlefield Education, →ISBN, page 41:

        If we agree with [Alan] Blinder's assessment, we must acknowledge the pressing need to inject new ideas into an old system—a system so antediluvian that it is, remarkably, still based on the agrarian calendar.

   2. Of attitudes, ideas, etc.: extremely old-fashioned, especially to a laughable extent; antiquated.

      Synonyms: (rare) antediluvial, (Britain, informal) out of the ark; see also Thesaurus:obsolete

      Antonyms: see Thesaurus:new

      Those ideas are antediluvian.

      • 1796, [Frances Burney], “A Chat”, in Camilla: Or, A Picture of Youth. […], volume III, London: […] T[homas] Payne, […]; and T[homas] Cadell Jun. and W[illiam] Davies (successors to Mr. [Thomas] Cadell) […], →OCLC, book V, pages 78–79:

        If, by any miſchance, and in an evil hour, ſome country couſin, not knovving my vvays, or ſome antediluvian prig, not minding them, happen to fall upon me vvith formal ſpeeches, vvhere I can make no eſcape, a fit of yavvning takes me immediately, and I am demoliſhed for the reſt of the day.

      • 2021 December 3, “LGBTQ Couples, Families and Marriage are ‘against the Natural Order,’ Thai Constitutional Court Rules”, in Coconuts Bangkok‎^[1], Bangkok, Thailand: Coconuts Media, archived from the original on 2023-03-19:

        Portions of the ruling reflected the court's culturally conservative roots, stating that because marriage is only for reproduction, LGBTQ relationships are unnatural because they cannot produce children. […] The ruling continued in its surprisingly antediluvian rationale, invalidating untold numbers of nontraditional families.

• antedeluvian (obsolete)

antediluvian (plural antediluvians)

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

   Synonym: prediluvian

2. (figurative, hyperbolic, chiefly humorous)
   1. A very old person.

      Synonyms: see Thesaurus:old person

      Antonyms: see Thesaurus:child

      • 1823 December 23 (indicated as 1824), [Walter Scott], “Discussion”, in St Ronan’s Well. […], volume III, Edinburgh: […] [James Ballantyne and Co.] for Archibald Constable and Co.; London: Hurst, Robinson, and Co., →OCLC, pages 134–135:

        From what cursed old antediluvian, who lived before the invention of the spinning-jennies, she learned this craft, Heaven only knows; […]

      • 1828 October, the Ettrick Shepherd [pseudonym; James Hogg], “The Brownie of the Black Haggs”, in Blackwood’s Edinburgh Magazine, volume XXIV, number CXLIV, Edinburgh: William Blackwood, […]; London: T[homas] Cadell, […], →OCLC, page 494, column 1:

        He was a boy in form, and an antediluvian in feature. Some thought […] that he was really and truly a Brownie.

   2. A person with extremely old-fashioned attitudes, ideas, etc., especially to a laughable extent; a fogey or old fogey.

• antediluvian on Wikipedia.Wikipedia

Borrowed from French antédiluvien.

antediluvian n (plural antediluvieni)

1. antediluvian