The Meaning of Liff was a humorous dictionary written by humorists and writers Douglas Adams and John Lloyd and first published in 1983. In the book, the authors took various place names and gave them definitions for common (and some not as common) things which needed a word. The book has proven popular, having been revised and expanded for the US market as The Deeper Meaning of Liff in 1990 and then revised again to a lesser extent in 2013 for the book's 30th anniversary. A supplement, a sequel, Afterliff by John Lloyd, and two spinoffs, The Yorkshire Meaning of Liff by Joe Moorwood and Liff Sentence by Craig Warhurst, have also been published. A number of translations have essentially expanded the concept into other languages.

liff, n. A common object or experience for which no word yet exists.