"If you call me a terrorist, then the argument to call me a terrorist is ad hominem," he writes in a statement posted on YouTube three weeks ago.
"Ad hominem," which is Latin for "to the man," is an argument directed against a person rather than his arguments.
In Loughner's video, titled "My Final Thoughts," the 22-year-old Tucson resident defines a terrorist as "a person who employs terror or terrorism, especially as a political weapon," a United Press International review of the video indicates.
He also says in the video that he "can't trust the current government" and that Americans "don't have to accept ... all the current treasonous laws."
"The government is implying mind control and brainwash on the people by controlling grammar," he says.
Officials in Tucson, where the shooting took place outside a supermarket where Giffords was meeting with constituents for a "Congress on Your Corner" event, did not speculate Saturday about what might have provoked the attack, which left 13 wounded.
Loughner identifies himself in the video as a U.S. military recruit at the U.S. Military Entrance Processing Command in Phoenix, which screens and processes applicants into the U.S. armed forces.
He says he "didn't write a (religious) belief on my Army application and the recruiter wrote on the application: None."
Neither the Phoenix command office nor the command's headquarters in North Chicago, Ill., responded to UPI requests for comment Saturday night.
Loughner's Tucson home had police cars outside it and was blocked off with police tape Saturday night, The Arizona Republic reported. Sheriff's deputies and FBI agents were standing guard.
Neighbors told the newspaper they knew Loughner, but not well.
Grant Wiens, 22, who said he went to high school with Loughner, described him as "kind of an interesting character" who kept to himself.
Ryan Miller, 19, said Loughner "seemed like a normal, everyday kid to me" who appeared to be "a jock, hanging out with the sporty kids."