Mentally quick and original
A signal that warns of imminent danger
To notify (someone) of imminent danger or risk
See syn. study at
How did you alert them?
He's always been so alert and in control.
"Keep me updated, and alert the neighboring sectors," he ordered.
He was willing to personally alert the local police and have them check out the vehicle even without clear cut identification.
Alex was alert for the rest of the ride, even noting a bear track once.