The word that you use when you literally cannot comprehend the amount of stupid that a person is. They are too dumb and so you have to resort to calling someone an idiot. It's that simple.
Or
It can be about when you get something wrong and realise it, or do a mistake.
Guy 1 - See that guy over there.
Guy 2 - Yeah? What about him?
GUy 2 - He is a straight up idiot! He added a 'd' in orange.
or
Girl 1 - Omg I dropped my phone, I'm such an idiot
Someone who uses the word “ratlicker” to define people who don’t like to wear the piece of crap that is know as a face mask.
What an idiot he just called me a “ratlicker” !