Definition of "forty-two"

"Forty-two!" yelled Loonquawl. "Is that all you've got to show for seven and a half million years' work?""I checked it very thoroughly," said the computer, "and that quite definitely is the answer. I think the problem, to be quite honest with you, is that you've never actually known what the question is."

1979, Douglas Adams, The Hitchhiker's Guide to the Galaxy