A zombie is an undead person in the Afro-Caribbean and Creole spiritual belief system of voodoo. These folkloric zombies are human bodies re-animated by supernatural means and shamanistic medicine to create dread among the living. Other more macabre versions of zombies have become a staple of modern horror fiction, where they usually engage in human cannibalism.
Colonel Jacob Wharton demonstrated voodoo techniques in 1995 to raise the dead. (TXF: "Fresh Bones")
In 2000, Fox Mulder and Dana Scully enlisted the aid of Frank Black to investigate murders that appeared to have connections with zombies and the Millennium Group. Mark Johnson, capable of necromancy, was indeed responsible for raising a number corpses back to life to engage in what he believed to be a battle at the imminent end of days. Mulder and Black were able to destroy all of the zombies. ("Millennium")
Zombie in The Lazarus Bowl
Later that year, Wayne Federman produced The Lazarus Bowl, a film starring Garry Shandling and Téa Leoni as Mulder and Scully, respectively, in their fight to stop the Cigarette Smoking Pontiff from creating a zombie army. The Smoking Pontiff's zombies were armed with sniper rifles. In discussion about the undead with Scully, Mulder surmised their compulsion to eat human flesh was based on a desire to do all things they couldn't do while alive. After that, zombies would do a lot of partying, but nobody was around long enough to see it. ("Hollywood A.D.")