A thought-form is in Hauntings, an artificial form that acts like a Ghost. In occultism, thought-forms arise from concentrated human thoughts and emotions expended in a place or they can be created deliberately by magic. An example of a haunting thought-form would be an artificial entity that seems attached to a battlefield, where intense emotional energy and mass dying occurred. Such an entity might take a human form or might be an undefined presence that conveys pain, suffering, or negative energy. A highly energized thought-form can exhibit a personality and seeming self-awareness.
Taken from :The Encyclopedia of Ghosts and Spirits– Written by Rosemary Ellen Guiley – September 1, 2007