a Nigga Excuse is just like a regular excuse, but is dumbed down into a form of Niggadome. Nigga excuses often stem from, but are not limited to, Nigga moments, i.e Nigga situations, which then require nigga excuses. Nigga excuses often times only make since to Niggas and the Niggas that come up with them.
Example of Nigga Excuse
Man 1 : " Yea i shot dat nigga!"
Man 2 : " Why?"
Man 1 : " dats nigga stepped on my fresh Jordan's" " I had just bought 'em"
Man 2 : " Word man, I would've did the same thing"