Means that someone is extremely nice and respectful. You would always want to be like them and respect them in every way possible. This is mainly used as a compliment, or a short word for, "Gotta go!"
2 examples.
Jimmy: "Wow i just wanna be like you, Alissa! You are such a huge Gyat!"
Alissa: "blushes," "Wanna make out?"
Jimmy: "whadafuk"