A response to something of obviously little importance when it is exclaimed otherwise.

An arrogant person who thinks or acts like they are way more important than they really are.

A person who is a big shit

This maybe either because they are your best friend and you like to annoy them
Or because they are just an annoying asshole.
It is most likely that the person calls you little shit

To trash talk someone a bunch of times.

When you get accused of murder and you have the big shit moment. Or when you take a big shit in the bathroom.

When someone looks like they're prone to taking huge dumps.

A dirty slag whore who also like to play with shit