n. A person who believes that the United States government perpetrated or allowed the terrorist attacks of September 11, 2001.
2009
The Iranian president is even a "truther," insisting that there was a hidden hand behind Sept. 11, 2001. "Could it be planned and executed without coordination with intelligence and security services — or their extensive infiltration?" he mused in the letter to Bush.
2009
The vote is likely to tear open old wounds as groups such as the "truthers", including actor Charlie Sheen who believe Americans have never been told the truth about what really happened on 9/11, try to persuade New Yorkers to open a new probe that would reinvestigate the attacks.
2006 (earliest)
Therefore, virtually every press release or statement about 9/11 should include a reference to the poll to show people that many Americans are 9/11 truthers who scoff at the 9/11 Commission as a fraud and that demand a real 9/11 investigation.
The term truther appears to be self-chosen. Jon Gold, an activist in the 9/11 Truth movement, wrote on his blog recently that the term originated in late 2004 when he was bucking up a fellow activist who "was tired of being ridiculed,” telling him, “You’re a 9/11 truther, don’t let them get to you.” Gold added, “In the back of my mind, I thought of the term ‘Quaker.’”