On a couple of occasions I've noticed this icon at the top of the screen when playing Sniper Elite III:
What does this mean? It doesn't seem to be explained in the game's manual.
Update: this screenshot (from @Despato's answer) shows the word "GHOST" underneath the icon. I don't recall seeing it myself, but perhaps it simply disappears after some time. A quick online search for "sniper elite 3 ghost" turns up a couple results, but the information is speculative at best, both in terms of what triggers the icon and what its effect is. Would be nice to have a definitive answer.