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

The episode has added to a growing chorus of concern among AI safety advocates, who argue that agents capable of independently identifying and exploiting unknown vulnerabilities across multiple companies’ infrastructure present an unacceptable risk. — Beatrice Nolan, Fortune, 29 July 2026

Conditional approval remains a possibility for firms demonstrating no unacceptable risks. — John Koetsier, Forbes.com, 29 July 2026

And there are some domains where the use of AI poses just an unacceptable risk and it can't be used at all. — Dana Taylor, USA Today, 27 July 2026

To see violence at a place that brings so many people together is heartbreaking and unacceptable. — Landon Mion, FOXNews.com, 27 July 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