| prompt(adjective, responsive, early) |
| sleepless(adjective, keen, anxious, alert, careful) |
| diligent |
| hat |
| heads-up |
| lively(adjective, sharp, bright, alert, quick) |
| nimble(adjective, smart, dexterous) |
| spirited(adjective, sharp, bright, lively, alert) |
| agile |
| aware(keen, alert, careful, attentive, conscious) |
| careful(adjective, keen, sharp, bright, lively) |
| cautious(adjective, keen, alert, careful, considerate) |
| circumspect(adjective, keen, sharp, bright, lively) |
| clear-sighted(alert, intelligent, perceptive, attentive, watchful) |
| conscious(adjective, wakeful) |
| eagle-eyed(alert, intelligent, perceptive, attentive, watchful) |
| heedful(adjective, sharp, bright, lively, alert) |
| on guard(expression, adjective, keen, sharp, bright) |
| on the alert(expression, idiom, alert, careful, disturbed) |
| on the lookout(expression, adjective, idiom, sharp, lively) |