Nihilism is characterized by an active, pervasive proclivity to discredit activities purported by others to have meaning. The nihilist’s energy and behavior flow from despair; he or she seeks the angry pleasure involved in destruction
Yalom, drawing on Maddi, defines nihilism as a clinically recognizable existential sickness — not philosophical skepticism but an active, destructive stance rooted in despair and masquerading as sophistication.
, Existential Psychotherapy, 1980thesis