O. D.—the officer of the day.
Officers Line, or Officers Row—the row of houses where the officers and their families live.
Old Issue—an old soldier.
Old File—an old officer.
Old Man—the company commander.
On Official Terms—not to be on speaking terms except officially.
On the Carpet—called before the commanding officer for admonition.
Openers—cathartic pills.
Orderly Buckle—a soldier when going on guard who strives by extra neatness of appearance to be designated as orderly for the commanding officer.
Orderly Room—company office.