noun. a philosopher who emphasizes freedom of choice and personal responsibility but who regards human existence in a hostile universe as unexplainable.
1. Noun, singular or mass There is no clear definition of existentialism, and as such the work that is classified as existentialist varies greatly. 2. Adjective Modernists’ questioning of philosophical Rationalism, which took for granted creation's underlying logic, also found support in the writings of Friedrich Nietzsche, whose existentialist philosophy held that reality originated and ended in individual experience.