2) The side-to-side nodding of the head with the non-verbal negative response to indicate resistance or disagreement with something.
3) A non-verbal response to a person's quick line of questions for self preservation reasons.
2) Dentist: I need for you to open your mouth, so I can take a quick look inside of it with this little device...
Child Patient: While nodding her head side-to-side with her mouth still closed and her arms crossed, she told the dentist, "Nn-hnn!!"
3) Lisa: Trey, my homegirl just told me that she saw you at the club last nite and you were all hugged up with another woman! Is this true, Trey?!?
Trey: Nn-hnn. You know that I was hangin' with my homeboys! Your girl didn't see me last nite!!!
Lisa: Are you lying to me, Trey!!!
Trey: Nn-hnn, I ain't lying!!!