1. To turn into a member of the living dead or undead: The young woman managed to get away from the sorcerer who had attempted to zombify her and, as a result, she was able to enjoy the rest of her life.
2. To deprive of energy or vitality: It was obvious that the screaming children were zombifying their parents.
3. To insert a system in a computer in order to send out spam: There are some computers that are taken over by hackers and zombified to perform malicious tasks and so become spam zombies.

A zombified computer is one that is controlled by another person without the owner's knowledge and used for sending spam or performing other illegal or illicit activities.