means A military operation in which an army surrounds a city, fortress, or stronghold and cuts it off, waiting and pressing until the defenders surrender or fall.

from From Old French 'sege,' meaning a seat — itself from Latin 'sedere,' 'to sit.' The logic is wonderfully literal: to lay siege was to sit down outside someone's walls and stay there. The same root that gives us 'sedentary' and 'session' gives us the deadliest form of waiting — an army parking itself at your gate and refusing to budge.