From the 1920s and onwards the German Nazis applied the term Entartete Kunst to pretty much all art from the avant garde art movements. E.g. expressionism. But even more conventional and traditional art was considered wrong and deemed unhealthy for the public to view. Any art which did not conform to Nazi goals and agendas failed the test. Much art was thus considered non-German, perverse, Jewish, Bolschewik and Communist by the National Socialist party. In summary the art was accused of degenerating German culture to a primitive and and unhealthy state of affairs.
Under direct supervision of Adolf Hitler, the art was confiscated and exhibited in Dresden, Weimar, Karlsruhe, Munich, Berlin and Stuttgart
The sole aim of the exhibitions was large-scale defamation of the art to prevent further and irreversible damage of society. The idea was to educate the public by showing exactly how bad and damaging the art was. In reality the scapegoating and displaying of Enteartete Kunst helped create respect for the avant garde movements. Ironically, then, Hitler acted as a great PR campaigner for degenerate art, though he wanted to achieve the opposite.
However, it was not all good news. The Nazis either pursecuted artists via Gestapo or disallowed them to work. Emil Nolde was officially banned from creating art, and much of Nolde’s work from period is called ‘unpainted paintings’. Emil Nolde’s water colours, drawings and oils were kept in hiding until the end of WW2.
So-called degenerate artists were: Emil Nolde, Heinrich Zille, Ernst Barlach, Otto Dix to name but a few.
See perhaps also article on expressionism.