an exploitable glitch is a video game glitch that players can use to gain an advantage. This is different from many video game glitches, which usually have no or even a negative effect on the players progress.
A note on exploitable glitches in MMORPGsEdit
Compared with single player games, while with exceptions, it is harder to say that a glitch from an MMORPG is an exploitable glitch. For example, in the case of Wall jumping in World of Warcraft, the designers often label use of that glitch as exploiting, when in reality, wall jumping does not usually give the player a direct advantage, but is usually quite harmless. In fact, the glitch can sometimes be quite inconvienent for the player. While I am not saying they can't be abused at all, the player is just usually trying to have some fun.