While this looks like a certain racial slur, it's really just a way of saying meager, stingy or ungenerous. If you get a niggardly share of cake, it means someone gave you a very small piece.
This word is so close to a nasty racial slur that people have gotten in trouble for using it correctly. The words are not related in any way, they just sound alike. If you use the word niggardly, and someone is taken aback or offended, they either misheard you or don't know what they are talking about. In this situation, aim for generosity. Don't be niggardly with patience and understanding of their ignorance.