vigilant
VIJ-uh-luntadjMeaning watchful and alert for danger or trouble
Memory hook a VIGIL: awake and watching all night. All night long the old owl keeps a vigil over the henhouse, eyes wide open, watching for foxes. She is vigilant.
The vigilant lifeguard never took her eyes off the water and spotted the struggling swimmer in seconds.
In context During the dry summer, rangers stayed vigilant, climbing the fire tower every hour to scan the hills for the first wisp of smoke.
Similar watchful, alert, attentive, on guard
Opposite careless, heedless, inattentive
From Latin vigilare, “to stay awake, keep watch,” from vigil (awake).