404

UK/ˈfɔːɹəʊˌfɔː(ɹ)/

adjective

Not found, especially of a web page on the Internet.

“Bill was 404 all morning.”

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Meanings

adjective404 (not comparable)
  1. not comparableslangcomputingNot found, especially of a web page on the Internet.

    Bill was 404 all morning.

noun404 (plural 404s)

plural 404s

  1. computingAn error indicating that a web page could not be found.

    Return 404s for all deleted pages. Some search engine marketers suggest redirecting old products to semantically related products instead of 404ing. This preserves link equity, whereas a 404 does not.

    2007, Cristian Darie, Jaimie Sirovich, Professional Search Engine Optimization with ASP.NET: A Developer's Guide to SEO, John Wiley & Sons, →ISBN, page 113
  2. NigeriacolloquialDog meat.
verb404 (third-person singular simple present 404s, present participle 404ing, simple past and past participle 404ed or 404'd)

present singular third person 404s · participle present 404ing · participle past 404ed · past 404ed · participle past 404'd · past 404'd

  1. computingTo return an error indicating that a web page could not be found.

    Return 404s for all deleted pages. Some search engine marketers suggest redirecting old products to semantically related products instead of 404ing. This preserves link equity, whereas a 404 does not.

    2007, Cristian Darie, Jaimie Sirovich, Professional Search Engine Optimization with ASP.NET: A Developer's Guide to SEO, John Wiley & Sons, →ISBN, page 113

Origin

From the HTTP error status code 404, meaning Not Found, returned by a web server responding to a request for a URL at which no resource exists.

Full word history & related roots →
Cite this entry
APA

404. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/404

MLA

“404.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/404. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “404,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/404.

Source: 404 on Wiktionary, CC BY-SA 4.0.