guard

a person who keeps watch over something or someone

the person who plays that position on a football team

• “the left guard was injured on the play”

a device designed to prevent injury

a posture of defence in boxing or fencing

• “keep your guard up”

the person who plays the position of guard on a basketball team

a group of men who escort and protect some important person

a precautionary measure warding off impending danger or damage or injury etc.

• “he put an ice pack on the injury as a precaution”
• “an insurance policy is a good safeguard”
• “we let our guard down”

the duty of serving as a sentry

• “he was on guard that night”

a position on the line of scrimmage

• “guards must be good blockers”

a position on a basketball team

to keep watch over

• “there would be men guarding the horses”

watch over or shield from danger or harm; protect

• “guard my possessions while I”

protect against a challenge or attack

• “Hold that position behind the trees!”
• “Hold the bridge against the enemy”

take precautions in order to avoid some unwanted consequence

• “guard against becoming too friendly with the staff”
• “guard against infection”