1. Reverse of a hard-on
2. When the sight of a disgustingly ugly piece of ass makes your dick want to curl back inwards in fear of its master whipping it out and taking it near that disgusting, ugly vajayjay.
A reference is like, Say you're having a conversation and you make a joke about like santa claus
That's referencing santa
Person 1: 'Haha *A Reference to dnf'
Person 2: 'SHUT THE FUCK UP OR I SWEAR TO SATAN I WILL PUNT YOU TO THE OTHER SIDE OF THE PLANET'
Person 1: 'No need to get touchy two.. haha. Please dont'