ex·is·ten·tial·ism    (ěg’zĭ-stěn’shə-lĭz’əm, ěk’sĭ-)  

n.  A philosophy that emphasizes the uniqueness and isolation of the individual experience in a hostile or indifferent universe, regards human existence as unexplainable, and stresses freedom of choice and responsibility for the consequences of one’s acts.