A person who adheres to the philosophy of existentialism.(noun)
Of or pertaining to existentialism.(adjective)
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Use "existentialist" in a sentence
"In all other things than atheism, now, I suspect the word existentialist fits me best- though the better read may correct me."
"He is a waste of time and energy. - see full assessmentJaspers- called existentialist- Amazingly, he actually believed that philosophy begins where reason ends."
"Indeed, this is what it means to be an existentialist, which is just another word for nihilist."