Source : Webster's Revised Unabridged Dictionary (1913)

Nigger \Nig"ger\, n.
   A negro; -- in vulgar derision or depreciation.

Source : WordNet®

nigger
     n : (ethnic slur) offensive name for a Black person; "only a
         Black can call another Black a nigga" [syn: {nigga}, {spade},
          {coon}, {jigaboo}, {nigra}]