Undefinable

"You cannot define electricity. The same can be said of art.
It is a kind of inner current in a human being, or something which needs no definition." -Marcel Duchamp

Three Duchamp brothers, left to right: Marcel Duchamp, Jacques Villon, and Raymond Duchamp-Villon in the garden of Jacques Villon's studio in Pateaux, France, in 1914. All three participated in the 1913 Armory Show in New York. Photographer unknown.  Smithsonian collection

Marcel Duchamp (28 July 1887 – 2 October 1968;    was a French artist whose work is most often associated with the Dadaist and Surrealist   movements. Considered by some to be one of the most important artists of the 20th century, Duchamp's output influenced the development of post-World War I Western art. He advised modern art collectors, such as Peggy Guggenheim   and other prominent figures, thereby helping to shape the tastes of  Western Art during this period.-Wikipedia