Green’s Dictionary of Slang

gyat(t) n.

[elision of god-damn n.1 ]

(US) a curvaious female posterior.

https://www.polygon.com 19 Oct. 🌐 The term ‘gyatt’ or ‘gyat,’ is a shortened version of ‘god damn’.
[Aus]Sydney Morn. Herald 18 Nov. 🌐 A gyat or gyatt is a ‘thicc’ (slang for curvaceous) bottom.