Wait a second Stefanie, I just gave you an example as to what my perception of a "demon" was.
If you want a direct answer to this question: Do you believe in the WTS definition of demons? I will give you a direct answer: No.
Now as to "supernatural beings", "ghosts", "spirits-be they good or bad", "poltergiests", "casper" and such? Well, personally by my own definition, I do believe that some of these exist. I can't prove it. There is nothing in the scientific world that has disproved it. So the possibility of such "entities" may exist, but I have no facts to give.
As to your experience, who could say? Perhaps it was a "spirit", perhaps not.
Some people who are or left the WTBTS are a bit...oh man, how can I say without getting in to trouble...skeptical? Is that good word to describe? Sure. They are skeptical because the WTBTS has this fetish about "Satan & His Demons". The concept of "demons" (by the WTBTS) is a tactic used in an over-dramatic way as to institute another little (actually a rather big) control practice.
Though I may not agree with them, I understand why they tend to fall in to sarcastic or trivial responses. Think about it for a second. Is there really any "meeting" you can recall where "Satan & His Demons" weren't brought up??? A conversation? The relentless preacy preach of how "Satan is the ruler of the world"? If you decided to think or do something that was questionable, no matter how trivial it may be, the universal counsel often had "Satan & His Demons" attached to it.
I understand why some here may scoff at the idea of "Demons", because of the inherint thought of how the WTBTS views them. In my opinion, the way the WTBTS utilizes "demons" as fear tactic is very silly to me. I can't help but chuckle at memories I have that involved discussions, counsel, talks, and dramas that were do over dramatic about "Satan & His Demons". It's become a eternal comedy routine where the funny just doesn't stop.
So, after being TRULY freed from the WTBTS, I understood that it was okay in this world to define "demons" as I see fit. Some agree, some don't. I like the ones that don't, their viewpoint offers the challenge and NEW perceptions to consider.