A zombie is a reanimated corpse, typically a human's. Stereotypical zombies are characterized by animalistic behavior, indifference to pain, and an insatiable hunger for human flesh (particularly brains). Some zombies walk with a stiff gait and outstretched arms due to rigor mortis. They are a common monster in horror fiction due to their predatory nature and tendency to shrug off debilitating injury.
Only characters with visible evidence of death or decomposition should be tagged zombie. Unnatural grayish-blue or green skin, blank eyes, and festering wounds are good indicators of when this tag should be used. Whether or not a character is canonically a zombie is irrelevant.