(a) Military = line of defence at defence, n. phrases 3 (now chiefly historical); (b) American Football the defensive players positioned on the line…

Military. A line of troops composed of men placed at detached intervals, to prevent passage to or from the guarded area; a chain of military posts…

Military. (a) A fortification, defence, or barrier formed by pickets, a stockade. Now rare. (b) The line or boundary guarded by a picket of soldiers.

Military. A defended boundary of a military position. Also: the boundary of a prison, airfield, civil airport, etc.