A poltergist is a spirit which is known to disturb a household. Poltergeists are known for all sorts of troubling habits, mainly causing objects to move or loud noises, as well as other phenomena.
Some poltergeists return to a certain household because they have a connection there. For example, a deceased family member may return to the house in which they lived in as a poltergist.
The word "poltergeist" is German for "noisy ghost".