warn or arouse to a sense of danger or call to a state of preparedness; "The empty house alarmed him"; "We alerted the new neighbors to the high rate of burglaries"
engaged in or accustomed to close observation; "caught by a couple of alert cops"; "alert enough to spot the opportunity when it came"; "constantly alert and vigilant, like a sentinel on duty"
quick and energetic; "a brisk walk in the park"; "a lively gait"; "a merry chase"; "traveling at a rattling rate"; "a snappy pace"; "a spanking breeze"
mentally perceptive and responsive; "an alert mind"; "alert to the problems"; "alive to what is going on"; "awake to the dangers of her situation"; "was now awake to the reality of his predicament"