A siege is a military strategy where an army surrounds a city, castle, or fortress and cuts it off from the outside world, waiting for the people inside to run out of food, water, or supplies and surrender. Instead of attacking directly, which might be too costly or dangerous, the attacking force essentially traps everyone inside until they can no longer hold out.

Throughout history, sieges could last months or even years. Medieval castles were built with thick walls, moats, and stockpiles of food specifically to withstand sieges. The defenders hoped their own army would arrive to rescue them, or that the attacking army would give up and leave. Meanwhile, the attackers might build siege towers to climb the walls, use catapults to hurl stones at the fortifications, or try to tunnel underneath.

The word can also describe any situation where someone feels trapped or under constant pressure. A family whose house is surrounded by reporters might say they're under siege by the media. A teacher whose students won't stop asking questions might joke that she's under siege at her desk. In these cases, siege describes the feeling of being surrounded with no easy escape, like those medieval castle defenders waiting behind their walls.