Jumping around and running into people while listening to music. It is usually done on the floor at a concert or in a mosh pit, as moshing in your seats can hurt quite a bit. Mostly done to harder music, as it is difficult to mosh to Jewel or Britney Spears. The best places to mosh are small venues that have no seats where everyone is really excited and can get a running start. My two favorite bands to mosh to are Nine Inch Nails and The Deftones.