Nihilism is the belief that all values are baseless and that nothing can be known or communicated. It is often associated with extreme pessimism and a radical skepticism that condemns existence. A true nihilist would believe in nothing, have no loyalties, and no purpose other than, perhaps, an impulse to destroy.
A Nihilist is a believer of nihilism which literally means "nothingism." They believe in nothing, maintaining that life has no meaning and rejecting all moral and religious values as well as political and social institutions.