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 previous time the New York Knicks won an NBA Final, in 1973, in-game sound was basically unheard-of in basketball—too distracting for players and fans. — Ellen Cushing, The Atlantic, 17 July 2026

The phenomenon reflects the recent evolution of the venture capital industry, the emergence of two extraordinary companies that have raised unheard-of sums of money, and the wide-open competition among them and others in AI. — Paresh Dave, Wired News, 5 June 2026

Jackson's stretch of debuts on the Billboard Hot 100 now includes seven decades – a nearly unheard-of feat, considering the tally was only introduced in the late '50s, about 10 years before Jackson and his brothers first appeared. — Hugh McIntyre, Forbes.com, 5 June 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