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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UNHEARD-OF Defined for English Language Learners

unheard-of

Definition of unheard-of for English Language Learners

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


UNHEARD-OF Defined for Kids

unheard-of

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

Definition of unheard-of for Students

: not known before an unheard-of invention


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