Its a truncated form of the original Australian slang for You Beauty! Used when a major win occurs or some occurence of great luck is vested upon an Australian.
My dog just got me a can of export from the fridge Ubewt!

Ubewt! My missus just told me she used to be a lesbian and her hot friend is coming to visit friday for action and Im allowed to watch.

Ubewt! Aliens just abducted our prime minister and we get to do another election.
by swiftyc April 30, 2019
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