Significance of this facial gesture in Korea?

Factual Questions
1

I was just watching a Korean film called “The Housemaid”, and there is a scene where a man is saying something to a (very angry and insulted) female character. In response, she bites her lower lip and juts her jaw forward in his direction. This shuts him right up in a way that intrigued me.

While the significance of this gesture was clear from the context as a sort of “fuck you” (and just intuitively it strikes me as aggressive), I’m curious as to whether this is a common gesture in Korea or elsewhere, and just how rude/insulting is it perceived to be (i.e. about the same as flipping the middle finger in the U.S. or much worse)?

2

I would say it’s a gesture of defiance, but nothing meant to be insulting (like the middle finger). It doesn’t strike me as a gesture with a clear definition - I know what you are describing, but it’s not a gesture that people would attach a specific meaning to.