The term ONE IN THE ARMY can be solved by two crossword solutions: SOLDIER (7 letters) and HUP (3 letters). A SOLDIER is a person who serves in an army, typically as part of a professional force. The term 'SOLDIER' is derived from the Middle English word soudeour, which comes from the Old French soudeer or soudeour, meaning 'one who serves'. HUP is an acronym for 'Halt, Up, and Pivot', a marching command used by the United States Army. It is used to indicate a change in direction while marching.