Emo was once a negative connotation on the new style of music created by such bands mentioned already (Fugazi, Rites of Spring, etc). Now it is an overly-hyped money making process, and has flooded the mainstream radio/tv stations. Trend following kids everywhere have adopted the "emo lifestyle" because it is the newest fad.
I want to cry while we have sex with each other.
A "fun" genre of music. Examples include Reel Big Fish, Mighty Mighty Bosstones, Catch 22 (although they are more of a swing dance style). And Ska without horns? What a horrible definition.
I love skankin'