Someone who believes that the "truth" about 9/11 is that it was an inside job. The internet is crawling with them.
That is the normal definition. When you get to a Ron Paul thread, the definition morphs into anyone who still has questions about the events that day and dares to say so.
We were warned by our founders to keep a watch on our leaders . Power corrupts and absolute power [like we seem have now ] corrupts absolutely .