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

The world has so many moving parts that extraordinary and even unheard-of things happen all the time. — Faye Flam, Scientific American, 7 May 2026

Doing groundbreaking, unheard-of things is becoming par for the course for Anthony. — Gabrielle Starr, Boston Herald, 26 Mar. 2026

This effort ultimately translated to a virtually unheard-of customer acquisition cost of less than one-half of one cent per new user. — Encyclopedia Britannica, 15 May 2026

This spring, at the end of our 58th season, 60 Minutes grew rapidly with an unheard-of 9% jump in viewers on CBS. — Joanna Ossinger,laya Neelakandan, CNBC, 3 June 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