It was like one of those bad dreams, when you are about to take an examination in an unknown subject after cutting classes all semester.

One was a known photograph of Mihdhar, the other a photograph of a then unknown subject.

An unknown subject was somebody to be identified and located.

He had many unknown subjects to protect as well as those who appeared before him.

Two books he started in 1892 but left unfinished were a comprehensive text on Russian music and a manuscript, now lost, on an unknown subject.

Your unknown subject has had contact with a corpse.

Maybe it's our unknown subject who seeks a mentor.

Unsub is an abbreviation for the unknown subject of an investigation.

We know the following things about our unknown subject.

Katie approached one of the women, had a brief conversation about some unknown subject, and then disappeared from view.