The Collaborative International Dictionary of English v.0.48:

jigaboo \jig"a*boo\ n.
   A negro, especially an African-American; -- an offensive term
   usually intended as an ethnic slur. [vulgar and offensive]

   Syn: nigger, spade, coon, nigra.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

jigaboo
    n 1: (ethnic slur) extremely offensive name for a Black person;
         "only a Black can call another Black a nigga" [syn:
         nigger, nigga, spade, coon, jigaboo, nigra]