A test for artificial intelligence suggested by the mathematician and computer scientist Alan Turing. The gist of it is that a computer can be considered intelligent when it can hold a sustained conversation with a computer scientist without him being able to distinguish that he is talking with a computer rather than a human being.
Some critics suggest this is unreasonably difficult since most human beings are incapable of holding a sustained conversation with a computer scientist.
After a moments thought they usually add that most computer scientists aren’t capable of distinguishing humans from computers anyway.
xkcd makes it even better with a cartoon on it. I love xkcd ! ;)