Something unknown. Someone who doesn't have a clue. Something that is missing. From the http code for unable to locate. "4-0-4 file not found".
He hasn't got a four-oh-four. Question: Do you know where you are? Answer: four-oh-four.
by james48843 November 26, 2010
1 more definition
A problem. Derivced from the Internet error message "HTTP 404: Page Not Found".
Jesus fuck, what's YOUR four-oh-four?
by Macavity October 30, 2003