Ganking usually implies a player or group of players using overwhelming force to kill an opposing player in Player vs. Player combat. A ganker is most often of a higher level, possesses superior gear, or waits for an opportunity to kill the target, such as when the target is low health or engaged with a mob.
Successful ganks usually consist of very short fights and depend on tactics like high burst DPS and the ability to hide, making rogues the archetypal ganker. Areas such as Stranglethorn Vale (known for this reason as "Ganklethorn Vale") and Hillsbrad Foothills are infamous for ganking, as they are locations that naturally overlap differently-leveled characters of opposing factions. With Cataclysm and the introduction of Archaeology, which induces high-level players to travel around Azeroth to find archaeological fragments, ganking has become a common and geographically widespread activity, especially in zones where dig sites overlap with areas where lower level players are questing, such as Stranglethorn Vale, Feralas, Desolace, and Azshara.
The word "gank" is a portmanteau of gang and shank.