Negation.
The same as "no".
To denny something, just more gently and cute.
Often used by weird people.
If it said by an otaku s/he may close her/his eyes and move her/his head from one side to another one.
Multi-purpose word that is used as a substitute for 'no', but is more subtle and nuanced. It can be used as a statement, exclamation, question, interjection and more.
Statement: Did you scream Timmy? Nuh.
Exclamation: Nuh! Stop it Timmy.
Question: Did you see Gobbles? Nuh. Nuh? Nuh.
Interjection: Nuh pardon me, but is that Timmy. Nuh. Nuh! Nuh? Nuh.