An old German term, which stands for American music.
Origin: During WWII, American soldiers brought their music to Europe where it was only enjoyed by open-minded folks, while the real Nazis called it Negerjazz.
Neger = offensive German word for an Afro-Whatever person.
Jazz = Jazz
The word Negerjazz can still be heard in various areas of Germany and Austria. Although it is mainly used by 'old' people (who used it already in the "good old days"), also younger generations say Negerjazz to describe Hip-Hop and related music genres.
Grandson: "I wanna have the new 50 Cent album for Christmas!"
Grandpa: "Who is 50 Cent? Is it Negerjazz?"
Grandson: "It is cool Hip-Hop from the U.S.!"
Grandson: "Uhm, yes, maybe."
Grandpa: "Forget it! I'll buy you some real music - German tuba music!"