Unacceptable means not good enough to be allowed. Unacceptable behaviour, an unacceptable delay, wholly unacceptable.
It is the standard word of official disapproval, and it does a great deal of work in policies, complaints and political statements precisely because it condemns without describing. Completely unacceptable and wholly unacceptable are near-fixed phrases. Note that unacceptable states a judgement rather than a fact, so the useful follow-up question is always unacceptable to whom, and what happens now.
1adjectiveunacceptableNot good enough to be allowed.
“The delay was unacceptable and it happened again the next month.”
synonyms: intolerable, inadmissible
unacceptable is a quality of not being allowed.
The word is un- plus acceptable, from Latin accipere, to receive — ad- plus capere, to take. Something unacceptable is literally something that will not be taken.
Proto-Indo-European
*keh₂p-
Middle English
unacceptabylle
English, today
unacceptable
From Middle English unacceptabylle, equivalent to un- + acceptable.
Etymology from Wiktionary, CC BY-SA