Definition of "Guard" :
noun: a position on a basketball team
noun: (American football) a position on the line of scrimmage
"Guards must be good blockers."
noun: the duty of serving as a sentry
"He was on guard that night."
noun: a precautionary measure warding off impending danger or damage or injury etc.
"An insurance policy is a good safeguard."
noun: a device designed to prevent injury or accidents
noun: a posture of defence in boxing or fencing
"Keep your guard up."
noun: a military unit serving to protect some place or person
noun: the person who plays that position on a football team
"The left guard was injured on the play."
noun: a person who keeps watch over something or someone
noun: the person who plays the position of guard on a basketball team
verb: watch over or shield from danger or harm; protect
"Guard my possessions while I'm away."
verb: protect against a challenge or attack
verb: to keep watch over
"There would be men guarding the horses."
verb: take precautions in order to avoid some unwanted consequence
"Guard against becoming too friendly with the staff."