What is a Metrosexual?

Now that David Beckham is constantly in the news the term metrosexual is being bandied about. Just what is a metrosexual? My dictionary is over ten years old and isn't going to be able to give me a definition.

Is it someone who only has sex in the city?
Or someone who only has sex with people who are not from the country?
Or someone like George W Bush who inflicts great damage to cities?