Punk-derived music that generall incorporates lots of time and tempo changes(imparting the "spastic" quality reffered to in the name). Skram, Prog, Metal, Free Jazz, and Grindcore are all (to varying extents) antecedant to it in terms of their influence. Spazzcore is often, while ostensibly chaotic, very demanding in terms of precision and physical endurance. The term was first applied to Frodus and Shelby Cinca is generally credited as the inventor of the term (which was originally inteded as an expiriment in marketing). Since the introduction of the term, however, it has taken on a life of it's own outside of it's original application.
BETTER KNOWN EXAMPLES OF SPAZZCORE
Dillinger Escape Plan