Not known or not widely known by name
He was at a loss to justify the unheard-of luxury of the Roman court.
The roll itself appears to be unheard-of before and after the 16th century, but other lists were current at least as early as the 15th century, as the duchess of Cleveland has shown.
Wholesale suppliers sometimes offer unheard-of bargains on bulk scrapbooking products.
It must not have been totally unheard of if they all understood what it was.
It.s unheard of.