1) Preposterously insane.
It can mean something that is insane beyond someone's wildest
imagination, to the point that it becomes contrary to reason or
common sense.
2) Something that is really hard to understand, which has to be repeated twice, or thrice before one fully comprehends it. (It can't be over 7 times, otherwise it would be: Unununderstandable.)
3) Something that is
unacceptable, and intolerable (esp. by whole societies, or religions.)
1: “Hey, Steve. Why is six afraid of seven?”
“
I don't know, Tim McGomnrey. WHY is six afraid of seven?”
“Cuz 7 8 9. Haha..”
“HAHAHA... WAIT... THIS IS UNUNDERSTANDABLE!!”
*****************
2: “And this is why Americans like potatoes.”
“Professor, can you repeat that last part 3 more times?”
*
The professor literally repeats it 3 more times*
“It's still ununderstandable, professor!”
“Get the &$@% out you
little piece of #%£¥!!”
*****************
3: “I said I wanted a decaf! This is NOT a decaf! This is irregularly ununderstandable on so many levels, you are ALL fired!!”