staff officer

a commissioned officer who is a member of a staff.

Origin of staff officer

First recorded in 1695–1705

I had a momentary mental picture of him as some Roman staff-officer rushing back to the base in his chariot.

Aliens |William McFee
The military chauffeur was not surprised either; nor was Captain de M., the French staff-officer who accompanied us.

In Morocco |Edith Wharton
I was on detached duty as staff-officer, and so got a leave of absence.

Miss Ravenel's conversion from secession to loyalty |J. W. de Forest
The staff-officer leads us half a mile to the right, where, sinking down utterly exhausted, we are soon sound asleep.

The Recollections of A Drummer-Boy |Harry M. Kieffer

Each of these in regular turn, as written on the list from which he calls them, a staff-officer ushers into the emperor's study.

Lippincott's Magazine, Volume 11, No. 26, May, 1873 |Various

staff officer

a commissioned officer serving on the staff of a commander, service, or central headquarters