adj. Not acceptable; unsatisfactory. un′ac·cept′a·bil′i·ty n.

Is there such a word as unacceptable?

unacceptable | Intermediate English

too bad to be accepted, approved of, or allowed to continue: These mistakes are unacceptable.

Is it unacceptable or not acceptable?

As adjectives the difference between nonacceptable and unacceptable. is that nonacceptable is not acceptable while unacceptable is unsatisfactory; not acceptable.