A word used by white people that is used as a substitute for the word "nigga". Usually thought to be less offensive than the actual word, it still will probably get you shot or beaten the hell up if used around a black person for any variation of the word "nigga" is considered offensive, no matter how or when it is used.
white kid:"yo, what up my nukka?"
black kid:"what'd you call me?"
white kid:"I said 'nukka' so its ok"
black kid:"I don't care how you said it, I'm still gon kick ya ass"