Guard

1. A person who, or thing that, protects or watched over something. Many Hollywood stars use armed guards for protection.
2. A squad responsible for protecting something. The National Guard does much important work.
3. A part of a machine which blocks access to dangerous parts. You must have a guard around the open gears.
4. (basketball) A relatively short player, playing farther from he basket than a forward or a center. The point guards should be nimble and fast.
5. (US Football) Either of two offensive positions between the center and each of the tackles, whose main responsibilities are to protect the quarterback, and open up "holes" through which offensive players can run. Guards should be heavy and strong to play that position.