- philosophy the doctrine that nothing actually exists or that existence or values are meaningless.
- relentless negativity or cynicism suggesting an absence of values or beliefs: nihilism in postwar art.
- political belief or action that advocates or commits violence or terrorism without discernible constructive goals.
- also nihilism a diffuse, revolutionary movement of mid-19th-century russia that scorned authority and tradition and believed in reason, materialism, and radical change in society and government through terrorism and assassination.
- psychiatry a delusion, experienced in some mental disorders, that the world or one’s mind, body, or self does not exist.