A zombie outbreak refers to a sudden and widespread occurrence of undead creatures, typically portrayed as reanimated corpses or bodies that are brought back to life by some unknown means. These beings are often depicted as being aggressive and seeking to feed on human flesh, causing chaos and destruction in their path. The phrase "zombie outbreak" is commonly used in fiction, particularly in the horror genre, but can also be used metaphorically to describe any sudden or overwhelming event that seems impossible to control or stop.