Unheard-of definition

ŭn-hûrdŭv, -ŏv
Not previously known; unknown.
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Without precedent; unparalleled.
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Highly offensive; outrageous or brazen.
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Not heard of before; unprecedented or unknown.
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Unacceptable or outrageous.

Unheard-of effrontery.

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Previously unknown; unprecedented.
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