1. A type of error message that one receives when the Internet address or site they're searching for cannot be found. I think this link is broken—it keeps giving me a 404 error.
2. By extension, a phrase used to indicate that one cannot answer a particular question. Sorry, 404—I have no idea.
phr. the answer to your question is unknown; the location you seek is unknown. (From the internet message: Error - 404 that is received when the internet cannot find the address you are seeking.) Q: Where’s the kitchen? A: 404. You’ll have to find it yourself.