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"
Bobby: " Im sorry, Gyat!"
Bill: "what"
When someone seems curvy woman or someone with a fat ass
Tyron : GYAT
Bill : “She got a fat ass”
GYAT is an acronym of "Get Yourself A Therapist" and it should be used when you see someone doing something stupid online.
"I think crocs are stupid!"
"GYAT"