One problem is that there are varying degrees of zombies, and there are different types of zombies. Zombies like those in 28 DAY and 28 WEEKS LATER are fast, furious and they still have some of their humanity, technically they aren't undead. Zombies like the ones in WARM BODIES can either be mummified horrors eating anything they can get their hands on, or they can be men and women hoping to revive themselves by falling in love and returning to the world of the living (beating hearts and all). Many zombies follow George A. Romero's zombies, slow, stupid flesh eaters, their only desire is to eat the living. It wasn't until RETURN OF THE LIVING DEAD that zombies wanted brains, not just living flesh. Even Romero changed his zombies with LAND OF THE DEAD and the zombies who were remembering little bits about who they were before they died. Then there is the origin of a zombie, a living being under control of a voodoo priestess or priest.
So, I find myself at a loss. There are so many varieties of zombies, and the only description I could think of to give a survivor was "still alive," yet that seemed too light. A survivor is a living breathing human, but a zombie who can return to the land of the living (like those in WARM BODIES), aren't they survivors as well? Can a zombie really be a living, breathing human being? How would you explain a zombie and a survivor to someone who had no idea what they were?