An individual from the upper-classes. A step up from the 'bourgies' of the affluent middle-classes.
Usually a noun, although can also be used as an adjective, and very occasionally, as a verb.
He plays croquet and still calls his dad 'daddy' at the age of 40, what a crat.
I suspected that she was from quite a bourgie family, it was only when I found out that her family live in a castle and go grouse hunting at the weekends that I realised that she's actually a fully-fledged crat.
You really should get your hair cut. Only Hugh Grant can pull off such a crat hairstyle.
The tranquil silence that reigns in the office is occasionally broken by the boss noisily cratting about the place in his blue blazer and chinos.