ni·hil·ism 
(nīə-lĭz′əm, nē-)
(nīə-lĭz′əm, nē-)n.
1. Philosophy The doctrine that nothing actually exists or that existence or values are meaningless.
2. Relentless negativity or cynicism suggesting an absence of values or beliefs: nihilism in postwar art.
3.
a. Political belief or action that advocates or commits violence or terrorism without discernible constructive goals.
b. 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.
4. Psychiatry A delusion, experienced in some mental disorders, that the world or one's mind, body, or self does not exist.
[Latin nihil, nothing; see ne in the Appendix of Indo-European roots + -ISM.]
nihil·ist n.
ni′hil·istic adj.
ni′hil·isti·cal·ly adv.