vigilant attentiveness; "he keeps a weather eye open for trouble"
the process of paying close and continuous attention; "wakefulness, watchfulness, and bellicosity make a good hunter"; "vigilance is especially susceptible to fatigue"
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"