un·known / ˌənˈnōn/ • adj. not known or familiar: exploration into unknown territory his whereabouts are unknown to his family. ∎  (of a performer or artist) not well known or famous.• n. an unknown person or thing: she is a relative unknown. ∎  Math. an unknown quantity or variable: find the unknown in the following equations. ∎  (the unknown) that which is unknown: our fear of the unknown.PHRASES: unknown to without the knowledge of: unknown to Miller, the police had taped their telephone conversation.DERIVATIVES: un·known·ness n.

unknown unknown god an unidentified god, especially one to whom an altar has been set up so no god would feel overlooked; in Acts 17:23, St Paul sees an altar in Athens with the inscription ‘to the Unknown God’, and proclaims to the Athenians that this God is in fact Jesus Christ.
Unknown Soldier an unidentified representative member of a country's armed forces killed in war, given burial with special honours in a national memorial; also called the Unknown Warrior. In Britain the tomb of the Unknown Soldier is in Westminster Abbey.