EXISTENTIALIST
existentialist
(adjective) relating to or involving existentialism; “existentialist movement”; “existentialist philosophy”; “the existentialist character of his ideas”
existentialist, existentialist philosopher, existential philosopher
(noun) a philosopher who emphasizes freedom of choice and personal responsibility but who regards human existence in a hostile universe as unexplainable
Source: WordNet® 3.1
Etymology
Noun
existentialist (plural existentialists)
A person who adheres to the philosophy of existentialism.
Adjective
existentialist (comparative more existentialist, superlative most existentialist)
Of or pertaining to existentialism.
Source: Wiktionary