1. sleepless Vigilant implies more sustained activity and more intelligent volition than alert; one may be habitually alert by reason of native quickness of perception and thought, or one may be momentarily Synonyms: vigilant, alert, cautious, on the lookout, wary, awake, circumspect, sleepless, watchful, careful, on the alert, wakeful, wide-awake Antonyms: careless, heedless, inconsiderate, oblivious, drowsy, inattentive, neglectful, thoughtless, dull, incautious, negligent, unwary
Synonyms for sleepless 
