What is a Movie?

I was reading an interesting article in the NY Times today, "In Defense of the Slow and Boring." In this article, two film critics, Manhola Dargis and A. O. Scott, from the Times talk about what is 'boring' in movies. Along the way, they ponder what the medium of movies really is. Is it pure entertainment? Is it educational? Can movies be high art ('cultural vegetables' as one critic put it)? And do the various aspirations of film directors and producers (for another discussion see, "Uneven Growth for Film Studio with a Message") matter when it comes to what a movie really is?

If the 'medium is the message', can a medium, such as a movie, ever really get past its status as entertainment (or money making venture)? Can movies be high art? Political motivators? Do they need to be anything more than action, speed and romance (e.g., this summer's Thor)? And does money or attention span have the final say about what kinds of movies can be made?

I have no answers, but I am intrigued... What is a movie?