404 /ˈfɔːɹəʊˌfɔː(ɹ)/noun 2adjective 1verb 1forms 4 noun2 •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 •(Nigeria, informal) Dog meat. adjective1 •(slang) Not found, especially of a web page on the Internet.Bill was 404 all morning. verb1 •To 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 forms404'd · 404ed · 404ing · 404s