Definition of white nigger:
(n) :
(slang, derogatory, offensive, ethnic slur) A white person who performs menial labor.
(n) :
(slang, derogatory, offensive, ethnic slur) A white person who campaigns or advocates against racial inequality.
(n) :
(slang, derogatory, offensive, ethnic slur) A black person who is perceived as deferring to white people.
(n) :
(US, UK, slang, derogatory, offensive, ethnic slur) An Irish person, especially an immigrant to the United States.
(n) :
(US, UK, slang, derogatory, offensive, ethnic slur) An Italian person, especially an immigrant to the United States.