What is Nnng!?
1.
The deep, drawn out, almost instinctive sound a person makes when they are being physically pleasured. Usually accompanied by eyes rolling to the back of the head while hands grasp for something to hold on to.
Could also be used as a word to imply what you would like to do to someone.
Nnng! That feels SO damn good!
or
That girl is so fine...Nnng!
See
2.
A cry of frustration and anger. Number of Ns may vary depending on the level of frustration.
George Clooney: Bob, I hope you did't mind me rubbing your girlfriend's thigh.
Bob: Nnnng!