Originating (presumably) on the World of Warcraft forums, this is an essentially derogatory concept some people employ that means that all that a certain class must do in order to achieve success in the game is to bind every key on their keyboard to one ability that is perceived to be overpowered, and then continue to roll their face across the keyboard. The notion is that this one ability is so amazingly overpowered in relation to those of other classes, all one has to do is absently spam it as much as possible (and they might as well do it with their face, because there isn't any other use for the big stupid thing on top of their shoulders).
Priest: waah waah I'm a little *!*%%
Warrior: Oh stfu -
1) bind every key on your keyboard to Flash Heal
2) faceroll
Tbh i Think this explains everything...