Origin: Latin suffix -able
Unacceptable has 6 different meanings across 1 category:
Something that is not acceptable.
"The manager marked his late submission as unacceptable and refused to grade it."
In plain English: There is no noun form of unacceptable; it is only an adjective used to describe something that is not allowed or good enough.
"No excuses are acceptable for such unacceptable behavior in this workplace."
not adequate to give satisfaction
"the coach told his players that defeat was unacceptable"
not acceptable; not welcome
"a word unacceptable in polite society"
"an unacceptable violation of personal freedom"
(used of persons or their behavior) not acceptable or reasonable
"impossible behavior"
not conforming to standard usage
"the following use of `access' was judged unacceptable by a panel of linguists; `You can access your cash at any of 300 automatic tellers'"
unsatisfactory; not acceptable
"The manager marked the report as unacceptable because it contained too many errors and lacked proper formatting."
In plain English: Unacceptable means something is so bad that you should not accept it at all.
"The waiting time for our table was completely unacceptable."
The word entered English from Middle French as inaceptable, combining the negative prefix with a form of "to accept." It was first used in the 16th century to describe something that could not be received or approved.