Word used to describe a woman's vagina. Usually associated with a man having sex with a woman. 'Nat King' is the short for 'Nat King Cole', an American Jazz singer, and this acts as a euphenism for the word 'hole' - a hole which symbolises a woman's vagina.
Billy: Alright man, you get your Nat King last night?
Danny: Aye man, she was fuckin' outstanding.
Billy: *Borat Voice* Aaaahhh-high five!