Imagine if you were trying to play Twenty Questions but weren't allowed to ask about the meaning of the word, only its position in the dictionary. Well somebody else imagined it first, wrote it up, and put it online.
It's called "Guess my word!", and each day there is a new word to guess.
You start by making some initial guess about where the word might be in the alphabet:
You find out where the word is with respect to your guesses (with the closest words being highlighted in blue and red (indicating before and after, respectively)):
And after a number of guesses, eventually you should converge on the word:
...after which you can enter your name to appear on the leaderboard and check out other people's times and guesses. It's a good way to work on your active vocabulary when you are not playing Bananagrams...
You can play Guess My Word by clicking here. If you really like it, there are now two separate words you can play each day. Plus there is a new iPhone app called Lexicographer which is a little different, and for which I have written a separate review.
The best thing about this game is that you can also easily play it offline as a two-person game. You can take turns thinking of the secret word and guessing, and since this can be played without pen and paper (as long as you can remember the two current bounding words), it makes a great game to play in the car.