Meaning of UNKNOWN in English

UNKNOWN

[noun] [U]Racism is in some ways just a fear of the unknown (= what is not familiar or known to you).An unknown is a person, esp. a performer or sports player, who is not famous.For her latest film she deliberately chose a cast of unknowns.(esp. US and ANZ) An unknown is also something that cannot be guessed at or calculated because so little is known about it.It's the big unknowns that make insurance companies uneasy.

Cambridge English vocab.      Кембриджский английский словарь.