Call of Duty: World at War: Zombies (also known as Call of Duty: Zombies) is a first-person shooter video game developed by Ideaworks Game Studio, and published by Activision for the iOS. It is a spin-off of the Call of Duty series, and based on the "Nazi Zombies" mode of Call of Duty: World at War. The game allows for multiplayer cooperative gameplay locally via an ad hoc Wi-Fi or Bluetooth network, or globally via the internet. It will offer purchasable downloadable content in the form of new maps in the future.
The game's setting originally takes place in a German bunker (Nacht der Untoten) during World War II from the viewpoint of a United States Marine. SS soldiers who have become zombies attempt to infiltrate the bunker and attack the player, and the player must defend themselves in the process.
Source: Wikipedia, "Call of Duty: World at War: Zombies", available under the CC-BY-SA License.