In WoW, I believe Ganking as a group of Horde/Alliance killing someone, since it's the only way to kill them, in a metephoric way of speaking.
And if someone 'ganks' you after respawning at your corpse, that's not the right term, the correct term is 'spawn rape'...Thanks
Person 1: Those damn horde keep ganking me!
Person 2: Well, I believe it's the only way to kill you.
Seeing as you may be a valuble threat to most people, they need to gank you inorder to kill you.