Something that is unmarked has no marking on it which identifies what it is or whose it is.
He had seen them come out and get into the unmarked police car.
He lies in an unmarked grave at Elmton.
3. adjective [usually verb-link ADJECTIVE, oft ADJ after v]
In a sport such as football, hockey, or basketball, if a player is unmarked, there are no players from the opposing team who are watching them in order to challenge them when they have control of the ball.
[British]
The striker was unmarked when he headed his second goal.
unmarked in British English
(ʌnˈmɑːkt)
adjective
1.
not carrying a mark or marks
an unmarked police car
2.
not noticed or observed
Examples of 'unmarked' in a sentence
unmarked
It was raining steadily by the time the two unmarked police cars reached Botany cemetery.
Cleary, Jon MURDER SONG (2002)
Then, just south of the Watertown exit, an unmarked car passed me.
Wood, Ted SNOWJOB (2002)
I dyed them red and black, and left an equal quantity unmarked.
Robin Hobb THE GOLDEN FOOL: BOOK TWO OF THE TAWNY MAN (2002)