unheard-of

adjective
un·​heard-of | \ˌən-ˈhərd-ˌəv, -ˌäv\

Definition of unheard-of 

: previously unknown especially : unprecedented moving at unheard-of speeds

First Known Use of unheard-of

1592, in the meaning defined above

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Time Traveler for unheard-of

The first known use of unheard-of was in 1592

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More Definitions for unheard-of

unheard-of

adjective

English Language Learners Definition of unheard-of

: not known to have existed or happened before : very unusual

unheard-of

adjective
un·​heard-of | \ˌən-ˈhərd-ˌəv, -ˌäv\

Kids Definition of unheard-of

: not known before an unheard-of invention

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