You could always Google... It's a minigame in Call of Duty: World at War.
What Is Nazi Zombies?
It is a Nazi who became a zombie, had they been a zombie who made the choice to then become a member of the Nazi party they would then be a zombie Nazi LOL
Its a mini game where youre plane crashes you killed a bunch of nazis you wake up in a bulding and go through waves of zombies buy guns and mutch more try to survive as many waves as posible