Well I don't think there's a clear way to define the term except as a fashion trend of goth and pop. For example, the long fringed bangs, hair dyed black but there are exceptions of course, form fitting shirts, and tight jeans for guys while the girls can wear anything as long as it looks gothic yet poppy like short skirts to show they have some pop in them, and hair dyed red and black to show that they're gothic.
Emo can also be defined as one who uses self destruction or depression for relief or attention. Emo, I think comes from the word emotions but used in a negative term of emotions such as angry, sad, and confused.
I sometimes use it a jokingly term like most people as someone who is seeking attention by posing the all above. In other words, one who finds it fashionable to use depression and poppy goth style for an excuse to be different. Funny thing is I happen to like some goth but I'm just not into pop so there are acceptions to this "rule."
I myself used to be a cutter but I never talked about it or showed it to people. In fact, I now find it embarassing by the scars. Yet since I'm sharing this story I guess that would sort of make me an emo.
I agree though, I think the word is overrated. I'm sick of hearing it myself since it doesn't clearly define anything.
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I live as I choose or I will not live at all.
~Delores O’Riordan