Poltergeist - A noisy ghost

Spirit - A being inhabiting or embodying a particular place, object, or natural phenomenon

Apparition - A ghostly figure

Benign - Of a kind and gentle disposition

Ectoplasm - The visible substance believed to emanate from the body of a spiritualistic medium during communication with the dead

EVP - A ghost or spirits voice on audio recording tapes. Typically there is no voice heard to the people present in the recording but after reviewing the tapes there are strange voices recorded. 

Ghost - The spirit of a dead person

Malevolent - Having or exhibiting ill will; wishing harm to others; malicious.

Phantom - A supernatural being, such as a ghost.

Phenomenon - Something having real, demonstrable existence

Orb - A sphere or spherical object.

Supernatural - relating to forces or beings that exist outside the natural world

Seance - A séance is a spiritual meeting to receive communications from the dead

.Specter - A supernatural being, such as a ghost.

Spectre - A supernatural being, such as a ghost.