an enclosing barrier around a city: the siege that shuts it in, or the fortification that walls it off for defense.
This word comes from the idea of hemming something in. It names the wall of confinement that surrounds a city, and the Bible uses it from two opposite points of view. When an enemy army throws its works around a town to starve it into surrender, that shutting-in is a siege. When a people builds a strong wall to keep enemies out, that same enclosing is a fortification.
Most often it is the siege: the long, grinding blockade that traps a city until its food runs out. The histories and the prophets use it for the great sieges of Jerusalem, and it carries all the horror those months held, including the famine that drove trapped parents to unspeakable acts.
A smaller group of verses turns the picture around and uses the same word for the defensive side: a fortified city, a protective rampart, or the lookout post a watchman stands on. Because English needs different words for the attacker's siege and the defender's wall, no single English word can cover the whole range. That is why the same Hebrew word surfaces in translations as siege, siege-works, stronghold, rampart, and fortified city.