A woman (or man) who is so stunning, beautiful, and gorgeous that one of those words just won't do when describing them. It is a term of endearment of the highest honor.
You walk into a room and see her/him.
Shawn: "Oh my God, has anyone ever told you how stuneautious you are?"
Steph: "Ummm no, is that a compliment?"
Shawn: "Hell yeah, it's like the ultimate compliment! I'm serious girl, you are just a stone cold fox. Stuneautious to the extreme!"
Steph: "Well thank you very much. You aren't so bad yourself"
Shawn: "Can I get your number?"