[quote=Darkraven]
I thought zombies don't exist in the media in The Walking Dead world
[/quote]
More specifically, it's that the works of George A. Romero were never made and so the concept of zombies was never popularized.

Hypothetically, it's not outside the realm of possibility that a video game would have undead corpses as enemies. I guess it wouldn't make much sense for Call of Duty to still have a mode where you kill hordes of undead, but it's not a huge deal. Just to be safe, never use the word "zombie" specifically.