Not heard; not perceived by the ear; as, words unheard by those present.
Not granted an audience or a hearing; not allowed to speak; not having made a defense, or stated one's side of a question; disregarded; unheeded; as, to condem/ a man unheard.
Not known to fame; not illustrious or celebrated; obscure.
Heard melodies are sweet, but those unheard are sweeter. John Keats
We're a very expensive group; we break a lot of rules. It's unheard of to combine opera with a rock theme, my dear . Freddie Mercury
Where I come from it was really unheard of to be at a party and someone says, 'What kind of music do you make?', and you say, 'Pop music.' You may as well have 'I'm not cool' stamped on your forehead. Lady Gaga
Jane Austen was an extraordinary woman; to actually be able to survive as a novelist in those days - unmarried - was just unheard of. Julie Walters