Most commonly used to denote a style of music that makes the Spice Girls look like Pantera. Men who listen to this generally are not men and could be beat up by five year old girls and their pet kittens.
This word is less commonly used to describe the type of people who listen to the aforementioned type of music. While these people certainly do suck, it is not all their fault...as they are only following the latest trend.
Dashboard Confessional is a perfect example of Emo
I went to visit my Emo friend today but he was too busy crying over the ant he had accidentally stepped on