Anybody who listens to I'm Sorry I Haven't a Clue on Radio 4 will know the game Mornington Crescent. There is now a multiplayer online version of this game courtesy of Microsoft and Cortana.

The latest version of Skype now has Cortana and is available on all platforms (Windows, Linux, Mac, mobile). When you receive a message you get helpful suggestions from Cortana for responses. The idea of the game is to get to the word “Indubitably”.
  I am online now
I am available now  
  Are you still around?
  What's your name?
What's yours?  
  I do not have one
You do now  
  I guess
Fair enough.  

The rules that are in use at any time are set by Cortana