A term used to describe fundamentalist "Christians" that believe in a literal interpretation of the Bible. These people have no concept of the cultural, historical and allegorical complexities present in the Bible. Fundies tend to be "sheeple" that repeat the ignorant rhetoric of their intolerant and improperly educated pastor. Some of their hallmark behaviors are taking Bible quotes out of context, and harassing people by asking them whether or not they have been saved. Not too polite about such things.
The fundie was befuddled by the allegories in the Book of Genesis, so he took the Creation Story literally.
Currently the term "Truther" refers to someone who adheres to the beliefs espoused by the 9/11 Truth movement. Truthers are conspiracy theorists that, like all conspiracy theorists, blatantly distort facts and quotes. These are the Bible thumpers of 9/11.
Some of them believe that the government orchestrated it in some complex, cockamamie scheme; others believe that the government simply let it happen.
Debating a Truther is like banging your head against a brick wall - painful and futile. You are likely to be called many things by them: ignorant, stupid, sheltered, blind, scared of the truth, a sheep, a lemming.