This is a much stronger and more elaborate use of the word no or na, it is usually used when angry and a loss of words comes to mind, this signifies no and rage, and a sign of short patience all in one
Kid: whattup douche
Kid 2: whattup man...
Kid: why is u such a fag bruh
Kid 2: .... Naaaa im just about sick and tired of your mouth
This is used when you don't want to answer with "Yes" because it will hurt the person's feelings but you also don't want to answer with "no" because that is a lie. It's mainly used with a boy who doesn't want to hurt his girl's feelings.