truther
n. A person who believes that the U.S. government perpetrated or allowed the terrorist attacks of September 11, 2001. Also: 9/11 truther, September 11 truther.

Example Citations:
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.
—David Ignatius, "Reading Iran by the Letter," The Washington Post, September 20, 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.
—Stephen Collinson, "New York reveals demands for new 9/11 probe may go to vote as Americans mark eighth anniversary," The Sunday Mail, September 13, 2009

Earliest Citation:
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.
—George Washington, "Social Proof," George Washington's Blog, May 22, 2006

Notes:
It looks like the word truther (or 9/11 truther) was first coined in 2004, accordingly to a recent column by the journalist and critic Leslie Savan:

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.'"
—Leslie Savan, "On Language: From Simple Noun to Handy Partisan Put-Down," The New York Times, November 18, 2009

Related Words: