Definition of "unmarked"

My mother died when I could not have been more than eight or nine years old, on one of old master's farms in Tuckahoe, in the neighborhood of Hillsborough. Her grave is, as the grave of the dead at sea, unmarked, and without stone or stake.

1855, Frederick Douglass, chapter 3, in My Bondage and My Freedom. […], New York, Auburn, N.Y.: Miller, Orton & Mulligan […]

The “little green men”—faces covered, wearing unmarked olive uniforms, speaking Russian and using Russian weapons—have played a significant role in both the occupation of Crimea and the civil war in eastern Ukraine.196

2015, Shane R. Reeves, David Wallace, “The Combatant Status of the “Little Green Men” and Other Participants in the Ukraine Conflict”, in International Law Studies, US Naval War College‎, volume 91, number 361, Stockton Center for the Study of International Law, page 393

Bale worked Bozovic again as he was left unmarked in the Montenegro area but could not get enough power on his header from a looping cross.

2011 September 2, “Wales 2-1 Montenegro”, in BBC‎