Definition of vigilant:
nimble, keenly aware, argus-eyed, on the ball, wakeful, lynx-eyed, keen-sighted, waking, alert, active, open-eyed, prompt, wide-awake, on the watch, hawk-eyed, study at watchful, light, wary, sharp-sighted, lively, quick-sighted, watchful, hustling, brisk, awareness.
- attentive (part of speech: adjective)
- vigilant (part of speech: adjective)
- "Lorna Doone, A Romance of Exmoor", R. D. Blackmore.
- "The Last Days of Pompeii", Edward George Bulwer-Lytton.
- "Studies from Court and Cloister", J.M. Stone.