(idiomatic) A person or thing whose nature or value is a mystery. / Used other than figuratively or idiomatically: see unknown, quantity.

The representative of military personnel who have died unidentified without proper burial, usually in war.

A certainty of unknown magnitude, consequence, structure, and probability characteristics; something that we don't know that we know.

An uncertainty of known magnitude, consequence, structure, and probability characteristics; something that we know that we don't know.

plural of unknown known

plural of known unknown

Synonym of as-yet-unknown

plural of as-yet-unknown

currently unknown

Something that is currently unknown.