Guard (noun)

1. A person or group of people who are responsible for protecting someone or something.
2. A person or thing that protects or prevents something from harm or damage.
3. A person who keeps watch and protects a place, building or equipment.
4. A defensive position in sports, especially in basketball.
5. A protective cover or sheath, as for a sword or knife.

Origin:

Middle english gard, from old french garde, from garder to guard; akin to old high german warda guardian.

Examples:

1. The museum hired a guard to protect the paintings.
2. The guard at the gate checked our tickets.
3. He played guard on the basketball team.
4. The knife has a guard to prevent the hand from slipping onto the blade.
5. The castle had a strong guard to protect it from invaders.