Definitions of alert

1. an automatic signal ( usually a sound) warning of danger

2. a warning serves to make you more alert to danger

3. condition of heightened watchfulness or preparation for action; " bombers were put on alert during the crisis"

4. An alarm from a real or threatened attack; a sudden attack; also, a bugle sound to give warning.

5. The lookout; a guarding against surprise; as, to be on the alert.

6. Alertness.

7. Alertly.

8. very attentive or observant; " an alert and responsive baby is a joy"; " 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"

9. mentally responsive; " an alert mind"

10. Watchful; vigilant; active in vigilance.

11. Brisk; nimble; moving with celerity.

12. On the watch; active; brisk; ready; vigilant.

13. Watchful: brisk.

14. On the watch; ready.

15. Watchful; brisk. Upon the alert, upon the watch.

16. Watchful; on one's guard; sprightly; nimble.