Dadaism

Dada was a literary and artistic movement born in Europe at a time when the horror of World War I was being played out in what amounted to citizens’ front yards. Due to the war, a number of artists, writers and intellectuals - notably of French and German nationality - found themselves congregating in the refuge that Zurich (in neutral Switzerland) offered. Far from merely feeling relief at their respective escapes, this bunch was pretty ticked off that modern European society would allow the war to have happened. They were so angry, in fact, that they undertook the time-honored artistic tradition of protesting.

Dadaism is the idea of inventing a new things or artworks. It is related to photomontage.
Here are some examples. 

Dadaist is the one who invented the idea first. The ideas usually not normal or not logical. They are not exist. But the world can accept the idea. For example dragon and unicorn. They are not even real.