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 or accidents

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 military unit serving to protect some place or 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"

(American football) 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'm away"

protect against a challenge or attack; "Hold that position behind the trees!"; "Hold the bridge against the enemy's attacks"

take precautions in order to avoid some unwanted consequence; "guard against becoming too friendly with the staff"; "guard against infection"