The word sack has several meanings:

1. A large bag made of strong material like burlap or canvas, used for carrying or storing things. Farmers might fill sacks with potatoes or grain. Santa Claus traditionally carries toys in a sack over his shoulder.
2. To fire someone from their job. When a company sacks an employee, they're telling that person they no longer work there. A coach might get sacked after a terrible season.
3. In American football, when a defensive player tackles the quarterback behind the line of scrimmage before they can throw the ball. A good pass rush leads to more sacks. The quarterback got sacked three times in the first half.
4. To destroy or plunder a city after conquering it. Historical accounts describe armies sacking cities during wars, stealing valuables and burning buildings. Ancient Rome was famously sacked by invading forces in 410 AD.