According to Wikipedia, "The Absurd" * refers to the conflict between the human tendency to seek inherent meaning in life and the human inability to find any. In this context absurd does not mean "logically impossible," but rather "humanly impossible." The universe and the human mind do not each separately cause the Absurd, but rather, the Absurd arises by the contradictory nature of the two existing simultaneously.
Absurdism, therefore, is a philosophical school of thought stating that the efforts of humanity to find inherent meaning will ultimately fail (and hence are absurd), because no such meaning exists, at least in relation to the individual. As a philosophy, absurdism also explores the fundamental nature of the Absurd and how individuals, once becoming conscious of the Absurd, should react to it.
Absurdism is very closely related to existentialism and nihilism and has its origins in the 19th century Danish philosopher, Søren Kierkegaard, who chose to confront the crisis humans faced with the Absurd by developing existential philosophy.
Absurdism as a belief system was born of the European existentialist movement that ensued, specifically when the French Algerian philosopher and writer Albert Camus rejected certain aspects from that philosophical line of thought and published his manuscript The Myth of Sisyphus. The aftermath of World War II provided the social environment that stimulated absurdist views and allowed for their popular development, especially in the devastated country of France. - End wikipedia quote
Absurdism is, in my personal opinion, a very individualistic philosophy. Some absurdist may not even be aware that there is an actual title for their philosophical views. Other absurdists may point out that even suggesting that a title be placed upon this view is absurd, or by taking a non-cognitive approach to the title suggest that such titles are meaningless. Albert camus regretted the continued reference to himself as a "philosopher of the absurd". To distinguish his ideas, scholars sometimes refer to the Paradox of the Absurd, when referring to "Camus' Absurd".
Absurdism has also been very influential in the creation of "'Pataphysics" (French: 'pataphysique). According to Wikipedia, 'Pataphysics is a philosophy dedicated to studying what lies beyond the realm of metaphysics. The term was coined and the concept created by French writer Alfred Jarry (1873–1907), who defined 'pataphysics as "the science of imaginary solutions, which symbolically attributes the properties of objects, described by their virtuality, to their lineaments." Jarry considered Hippocrates of Chios and Sophrotatos the Armenian as the fathers of this "science". A practitioner of 'pataphysics is a 'pataphysician or a 'pataphysicist. - End wikipedia quote