unheard-of

adjective

un·​heard-of ˌən-ˈhərd-ˌəv 

-ˌäv

: previously unknown

especially : unprecedented

moving at unheard-of speeds

Synonyms of unheard-of

• unprecedented
• novel
• strange
• unfamiliar
• new

Examples of unheard-of in a Sentence

houses selling at unheard-of prices

Recent Examples on the Web

That is unheard-of with prolonged exposure, cognitive processing, and certainly SSRIs, the current standard-of-care options. — Anderson Cooper, CBS News, 16 Aug. 2026

To fix the problems at the factory, the company would team up with yet another unheard-of partner promising technological innovation. — Jesse Coburn, ProPublica, 12 Aug. 2026

The darling of the screen charmed audiences around the globe, but had a tough time making love and romance work with her unheard-of level of stardom. — Angela Andaloro, PEOPLE, 12 Aug. 2026

The damage forced an almost unheard-of response from the grain trade itself. — Ingmar Rentzhog, Forbes.com, 1 Aug. 2026

Word History

First Known Use

1592, in the meaning defined above

Kids Definition

unheard-of

adjective

un·​heard-of

-ˌəv, 

-ˌäv

: previously unknown : unprecedented

moving at unheard-of speeds