When I’m in a conversation, and I get annoyed or fed up, I use “whatever”. It means shut up, because I’m tired of your stupid crap, or your thick headedness.
I means I’m tired of you judging me, when you have no right to. It means you’re making me angry, and I don’t feel like snapping. It means I want to tell you to fuck off, but not permanently.
So, a “whatever” from me is a warning. That if you keep pushing, I am likely to blow up. A “whatever” from me means that I am done with the current conversation. I am an easy going person, but I have my limits. “Whatever” means I have reached that limit. So tread lightly.