What is a poltergeist?

A poltergeist ("noisy ghost" or "noisy spirit" from German) is a type of ghost or spirit that is responsible for physical disturbances, such as loud noises and objects being moved or destroyed. They are purportedly capable of pinching, biting, hitting, and tripping people. Most accounts of poltergeists describe the movement or levitation of objects such as furniture and cutlery, or noises such as knocking on doors.