An electronic dance that originated in Europe, specifically the Netherlands and Germany. It involves swinging your arms and legs back and forth to a variety of sub genres of hardstyle/techno stuff. One popular Jumpstyler is Patrick Jumpen. Look him up on youtube, he has some good tutorials.
Guy 1: Hey guy 2, what are you doing?
Guy 2: I'm dancing Jumpstyle!
Guy 1: Cool! I'll join you! (dancing commences)