| obedient(correct, alert, intelligent, perceptive, attentive) |
| observative(adjective, correct, sympathetic, alert, intelligent) |
| on the job(expression, idiom) |
| on toes(expression, adjective, correct, sympathetic, witting) |
| open-eyed |
| openmouthed |
| penetrating(correct, alert, intelligent, perceptive, attentive) |
| perceptive(alert, intelligent, attentive, watchful, discerning) |
| questioning(correct, alert, intelligent, perceptive, attentive) |
| quick(alert, intelligent, perceptive, attentive, watchful) |
| searching(correct, alert, intelligent, perceptive, attentive) |
| sensitive(correct, alert, intelligent, perceptive, attentive) |
| sharp(alert, intelligent, perceptive, attentive, watchful) |
| sharp-eyed(adjective, correct, sympathetic, alert, intelligent) |
| surveying(correct, alert, intelligent, perceptive, attentive) |
| understanding(correct, alert, intelligent, perceptive, attentive) |
| vigilant(alert, intelligent, attentive, watchful, sharp-eyed) |
| wide-awake(alert, intelligent, perceptive, attentive, watchful) |
| wide awake(expression, adjective, correct, sympathetic, witting) |
| Delphian |