Define Existentialism

Existentialism is a European  philosophy that focuses on the individual human being's experience and recognition of and triumph over the meaninglessness of existence. It is a revolt against traditions and conversations- religious, moral, political, legal, ethical, economic etc. and attempt towards man's true freedom. It emphasizes individual uniqueness, freedom, and responsibility in opposition to various forms of determinism, its name deriving from the principle that 'existence precedes essence': that is human choices are not dictated by a determining essence or fixed human nature.

Rooted in the thoughts of nineteenth and early twentieth-century figures  such as Soren Kierkegaard, Friedrich Nietzsche, Fyodor Dostoevsky,  and Franz Kafka,existentialism became widely influence in the 1940s, especially after the horrors of World War II, through the novels, plays and philosophical writing of Jean Paul  Sartre. Other notable exponents of existentialism  are Gabriel Marcel, Albert Camus, Samuel Beckett, Eugene Ionesco, Jean Genet and Harold Pinter, According to the existentialism man is because he exists, 

Man is more important that all rules, regulations, laws, principles or values, Man's existence is essentially miserable, lonely, alienated : the desire for happiness is a myth. Thus the existentialists regard human life as absurd or meaningless.