Does the word "ununderstandable" exist?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hi,
What is the antonym of “understandable”? Does the word “ununderstandable” exist?

Many thanks
Nessie

2

incomprehensible
unintelligible

And some others, depending on what you mean.

3

“Ununderstandable” would be understandable, though perhaps as a slightly jocular formation; but “incomprehensible” would be the usual word.

MrP