a genre which has lost its meaning over the years and now currently consists of mostly 14-19 year olds, mostly consisting of wearing black clothes, tight ripped pants (if you're a guy) or short slutty skirts with fishnet stockings (if you're a girl), hair worn in a certain retarded manner, jewelry from Hot Topic, requires listening to Dashboard Confessional, etc. These people all strive to be unique but somehow all end up the same. It is easy to identify an emo by the typically downcast look, hair combed over half the face, and real (or fake) cut marks on their arms. 95% of the people thrown into this class get off on creating drama around them, whileas in all reality their lives are not that bad. Typically "misunderstood" by anyone not in their clique (meaning the rest of civilized humanity), they often misconstrue themselves as aspiring geniuses, poets, artists, etc. see also delusions of grandeur
for insight on the common emo's thought process. These people usually grow out of this stage by age 18 or 19, realizing that in all reality, the world does not give a fuck if your puppy died when you were 12...and it was the only real friend you had.
Emo: "my puppy died when i was 12, it was the only real friend that i ever had that understood me *cut cut*"
Common Person: "wow, you're...pathetic."