What is the meaning of guard?

noun

• A person who keeps watch over something or someone.
• The person who plays that position on a football team.
  • usage: "the left guard was injured on the play"
• A device designed to prevent injury or accidents.
  • synonyms: safety, safety device
• A posture of defence in boxing or fencing.
  • usage: "keep your guard up"
• The person who plays the position of guard on a basketball team.
• A military unit serving to protect some place or person.
• A precautionary measure warding off impending danger or damage or injury etc..
  • usage: "he put an ice pack on the injury as a precaution"; "an insurance policy is a good safeguard"; "we let our guard down"
  • synonyms: precaution, safeguard
• The duty of serving as a sentry.
  • usage: "he was on guard that night"
  • synonyms: guard duty, sentry duty, sentry go
• American football. ( a position on the line of scrimmage)
  • usage: "guards must be good blockers"
• A position on a basketball team.

verb

• To keep watch over.
  • usage: "there would be men guarding the horses"
• Watch over or shield from danger or harm; protect.
  • usage: "guard my possessions while I'm away"
  • synonyms: ward
• Protect against a challenge or attack.
  • usage: "Hold that position behind the trees"; "Hold the bridge against the enemy's attacks"
  • synonyms: defend, hold
• Take precautions in order to avoid some unwanted consequence.
  • usage: "guard against becoming too friendly with the staff"; "guard against infection"