Definition of truther
: one who believes that the truth about an important subject or event is being concealed from the public by a powerful conspiracy
- He isn't a 9/11 truther, as some erroneously allege, but he has his fair share of "out there" beliefs.
- —Felix Blederman
- But it is not flattering to be called a "truther." The term originated, as far as anyone can tell, to characterize people who embraced alternative explanations for the Sept. 11 attacks.
- —Mark Leibovich
