A dance style originating in the 1980's characterized by fast heel and toe twisting and stepping, running man variations, stomping with the beat, foot swiveling from side to side, and having feet that appear to be gliding on and off the ground.
Shuffling is mostly for the feet and the arms just compliment whatever foot motions are taking place. This dance style is very high paced, intense cardio, and is usually to done to music with a constant beat such as electro, hardstyle, and/or techno.
Shuffling is preferrable in shoes as it won't hurt your feet, but also acceptable in socks or barefoot. Outfit and clothing style are irrelavant. Many shufflers (anyone who is decent or better at shuffle dancing) gain popularity by dancing in public, at meetups, but mostly by posting videos of them shuffling online.
After watching other amazing shufflers, you will most likely want to learn how to or at least want to obsessivly watch others shuffle because it looks cool.
A: "Holy shit dude what's that guy doing?! It looks like he's floating on air while stomping to the music!"
B: "Yeah, he's just shuffling"
A: "DAMN! I want to be able to do that some day!"