The belief that life is meaningless, and therefore rejecting all religious and moral principles.
From nihilism stems optimistic nihilism: a nihilistic approach towards life through the lens of hope. In other words, finding peace and comfort in the fact that nothing matters. Most people in the world in the world either heavily accept or reject this ideology.
It dangerous to be optimisically nihilist. It is a vortex ideology that quickly sucks one’s inate curiousity and depth as a human being. It attempts to block attempts of deep understanding of everything inside and around oneself just because it may not matter. In the end, this leads to a very shallow personality, see The compounding effect of lazy decision-making. I know from experience.
In truth, it is probably best to strike some balance between nihilistic ideas and our “default settings”. For me, this has been quite difficult.