The Collaborative International Dictionary of English v.0.48:

greaseball \grease"ball\ n.
   a person of Italian descent; -- used as a derogatory ethnic
   slur, and considered offensive. [offensive slang]

   Syn: wop, dago, Guinea.
        [WordNet 1.5] Grease cock

WordNet (r) 3.0 (2006):

greaseball
    n 1: (ethnic slur) offensive term for a person of Italian
         descent [syn: wop, dago, ginzo, Guinea,
         greaseball]