(Does anyone else have a hard time remembering the definition of existentialism?)
princeton.edu: (philosophy) a 20th-century philosophical movement chiefly in Europe; assumes that people are entirely free and thus responsible for what they make of themselves.
Answers.com: 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.
Merriam-Webster: a chiefly 20th century philosophical movement embracing diverse doctrines but centering on analysis of individual existence in an unfathomable universe and the plight of the individual who must assume ultimate responsibility for acts of free will without any certain knowledge of what is right or wrong or good or bad
Wikipedia: a philosophical movement which posits that individuals create the meaning and essence of their lives, as opposed to it being created for them by deities or authorities or defined for them by philosophical or theological doctrines.
Wiktionary: A twentieth-century philosophical movement emphasizing the uniqueness of each human existence in freely making its self-defining choices, with foundations in the thought of Soren Kierkegaard (1813-55) and Friedrich Nietzsche (1844-1900) and notably represented in the works of Karl Jaspers (1883-1969), Gabriel Marcel (1887-1973), Martin Heidegger (1889-1976), and Jean-Paul Sartre (1905-80).
All About Philosophy: There is a wide variety of philosophical ideologies that make up existentialism so there is not a universal existentialism definition. It is necessary to remain open and realize that most existentialists have a different view and form.
(Hee hee. Of course they do.)