Correct spelling


Correct spelling, explanation: indisputable may seem complicated, as there are two suffixes, and the structure is as follows: in + dispute + able, but fortunately, it’s rather regular. The only complication is that the e in dispute is omitted, but it’s because in English we generally shorten ea to just a, so the word’s spelling is indisputably indisputable.

Definition of indisputable:
1. not to be questioned, certain
There is no indisputable evidence of the existence of UFOs.
Albert Einstein is considered to be an indisputable math genius.

Incorrect spelling


Incorrect spelling, explanation: suffixes -able and -ible have the same meaning, so you may be unsure which one to use. In the case of words where there is a base word, which, in this case, is dispute, it’s correct to use able. In the case of words that do not work independently (like ed in edible), it’s proper to use -ible. By this logic, indisputible is incorrect, and the only correct spelling is indisputable.