Duping in this case is when the player takes 1 item example a 400% exp scroll and does some voodoo magic trick to make it a stack of 25s of the same scroll then repeat repeat repeat till you have a guild bank full of them. Another way is making a lets say a Benezar Helmet have 20% all atk, DD, Atk Spd or w/e stats you want to add to it. Yes all this examples are hacking.
This should give you an idea of what we are talking about.
LacieLane 135 Wizard
Priestess 128 Priest
Quit!!!
that was awesome!!