1)a kinky sexual practice. in a good way.
2)someone who indulges in such a practice. in a good way.
"Hey, did you see that video my girlfriend sent me on youtube? that was freakynasty!
she showed her tittums and everything..."
"You are a freaknasty nymphomaniac...and i like it."
"Two freakynasty girls walk in to a bar, and everyone gets laid but it was the best time of their life."
"Vin Diesel is freakynasty."