a belief in the pointless of existance. the absence of truth. the absence of reason.
those who see it as a self-defeating argument are people who still have something to believe in.
despite the universe being so mind-numbingly complex and consciousness itself being so much of a mystery, many people actually believe that nihilism is invalid because the 'logic' possessed by what we think of as our consciousness doesn't allow it to make sense.
a christian might argue that god must exist because there must be some infinite force in the universe. they would then argue that god is the creator of all life, and that things like logic come from god, and in fact are a part of god (as he is infinite). unfortunately, this is also self-defeating, because by using logic to prove the existance of god (and thus logic) is just as absurd as nihilism. this, in turn, leads to the logic that nothing can be known. this then continues and endless loop of logic and anti-logic, making existance seem pointless, insane, and absurd. and THAT is what nihilism really is.
Nietzsche is commonly associated with nihilism, although from what i've been able to figure out without actually studying it in school (while researching it in my spare time), he was not a nihilist himself. rather, he seems to be more of someone who defined it and contemplated the intricacies associated with it.
, creator of nine inch nails
is generally considered to be a true nihilist, which is represented by the lyrics, feeling, and sound of his music. even nothing records
, a record company started by reznor, embraces this concept in its name.