7. (noun)precaution, safeguard, guard 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"
8. (noun)guard duty, guard, sentry duty, sentry go the duty of serving as a sentry "he was on guard that night"
9. (noun)guard (American football) a position on the line of scrimmage "guards must be good blockers"
11. (verb)guard to keepwatchover "there would be men guarding the horses"
12. (verb)guard, ward watchover or shield from danger or harm; protect "guard my possessions while I'm away"
13. (verb)defend, guard, hold protect against a challenge or attack "Hold that position behind the trees!"; "Hold the bridge against the enemy's attacks"
14. (verb)guard take precautions in order to avoid some unwanted consequence "guard against becoming too friendly with the staff"; "guard against infection"
Definition of 'guard' 
