Poltergeist

A poltergeist (help·info) (from German "poltern", which means "rumble" or "make noise", and "geist", which means "ghost", "spirit" or "embodiment") is a spirit or ghost that is able to move and influence objects. Poltergeists are said to be invisible.

Poltergeists are said to bother only one person at a time. This person is called their "focus".^[1] Poltergeists will bother only their focus. They are said to only last a few weeks, then will move on to another target. Often poltergeists are reported around children and adolescents. Some scientists think that poltergeists only exist in a person's head as a result of psychokinesis. They think that the "poltergeist effect" is a result of mental trauma.

1. ↑ Guiley, Rosemary Ellen (1991). Encyclopedia of the Strange, Mystical & Unexplained. New York: Gramercy Books. ISBN 0-517-16278-4.