unheard of

unheard of adjective atypical, different, exceptional, exemplary, extraordinary, first, first ever, improbable, matchless, never before encountered, new, not to be expected, novel, of its own kind, original, out of the ordinary, out of the pale, out of the way, rare, sensational, singular, strange, surprising, tremendous, unaccustomed, uncommon, uncustomary, unequaled, unexpected, unfamiliar, unheard of, unique, unmatched, unparalleled, unprecedented, unnhought of, unusual

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See also: extraordinary, implausible, ludicrous, noteworthy, novel, original, peculiar, portentous, prodigious, uncanny, uncommon, unprecedented, unusual