"Spirit Intrusion"

While relating the ghost encounters at work, someone referred to the ghost as a "spirit intrusion." I had never heard that term before. I wanted to ask this person about it but the situation wasn't right. "Spirit intrusion." From the brief on-line searching I did, it seems to be a term or concept related to Shamanism and the chakras. Here it's described, not in terms of ghosts, but a physical ill within one's body. 

Here's something (scroll down a bit) concerning some Native American traditions. Like the above, it concerns the physical body and ills, with spirit and souls being the invasive cause.

While I'm unfamiliar with this concept of "spirit intrusion" I'm not so sure the ghost in this case is a case of what a colleague said about spirit intrusion. I think this person meant all ghosts are "spirit intrusions" and I'm not sure really what she meant. I had the feeling she believes all "ghosts" are manifestations of unease that are heavily tied in with the observer. If I get the opportunity I'd like to discuss this and find out more with this person. In the meantime, this is a new and interesting path to explore.