It’s one hell of a long definition and something that I can’t effectively put in my own words so I’ll let Wikipedia do the talking for me:
Dada or Dadaism is a cultural movement that began in Zürich, Switzerland, during World War I and peaked from 1916 to 1922. The movement primarily involved visual arts, literature—poetry, art manifestoes, art theory—theatre, and graphic design, and concentrated its anti war politics through a rejection of the prevailing standards in art through anti-art cultural works. Dada activities included public gatherings, demonstrations, and publication of art/literary journals; passionate coverage of art, politics, and culture were topics often discussed in a variety of media. The movement influenced later styles like the avant-garde and downtown music movements, and groups including surrealism, Nouveau Réalisme, pop art, Fluxus and punk rock.
You can now consider yourself enlightened. :o)