unacceptable

adjective

un·​ac·​cept·​able ˌən-ik-ˈsep-tə-bəl 

-ak-

: not acceptable : not pleasing or welcome

unacceptability

ˌən-ik-ˌsep-tə-ˈbi-lə-tē 

noun

unacceptably

ˌən-ik-ˈsep-tə-blē 

adverb

Synonyms of unacceptable

• wrong
• poor
• lame
• bad
• horrible
• terrible
• deficient
• awful
• unsatisfactory
• flawed
• disastrous
• pathetic

Examples of unacceptable in a Sentence

a word that is unacceptable in formal English

Some of her ideas were unacceptable to other people.

Recent Examples on the Web

Added to this, crews are finding ways to get around this unacceptable situation by ignoring alarms and even rewiring systems so the alarms never sound in the first place. —New Atlas, 24 Jan. 2026

Any violence against a judge or a judge's family is completely unacceptable. —Sarah Lynch Baldwin, CBS News, 23 Jan. 2026

The European Union’s defense commissioner raised the prospect of a 100-thousand strong European army in a January speech, an idea previously dismissed as unworkable and political unacceptable in the bloc. —Clare Sebastian, CNN Money, 22 Jan. 2026

For a game as complex and fast-paced as professional football, this lack of year-round preparation is unacceptable. —Steve Forbes, Forbes.com, 22 Jan. 2026

Word History

First Known Use

15th century, in the meaning defined above

Rhymes for unacceptable

• acceptable
• perceptible
• susceptible
• imperceptible

Kids Definition

unacceptable

adjective

un·​ac·​cept·​able ˌən-ik-ˈsep-tə-bəl 

-ak-

: not acceptable : not pleasing or welcome

unacceptably

-blē 

adverb