unheard-of
[ʌnˈhɜ:rd ʌv]
adj.
前所未闻的，无先例的，空前的;
旷古未闻;
例句:
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Find out more about our use of this data.
来自BBC
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Lots of people will be shocked by the result.
来自BBC
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Let's hope for a fantastic week of tennis!
来自BBC
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He'd dyed his hair, which was almost unheard-of in the 1960s.
他染了头发，这在20世纪60年代是罕见的事。
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We are developing our production at a speed unheard - of before.
我们正以前所未闻的速度发展生产.
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What he said is really an unheard - of fantastic story.
他讲的真是千古奇闻.