Source : Webster's Revised Unabridged Dictionary (1913)

Wakeful \Wake"ful\, a.
   Not sleeping; indisposed to sleep; watchful; vigilant.

         Dissembling sleep, but wakeful with the fright.
                                                  --Dryden.
   -- {Wake"ful*ly}, adv. -- {Wake"ful*ness}, n.

Source : WordNet®

wakeful
     adj 1: carefully observant or attentive; on the lookout for
            possible danger; "a policy of open-eyed awareness";
            "the vigilant eye of the town watch"; "there was a
            watchful dignity in the room"; "a watchful parent with
            a toddler in tow" [syn: {argus-eyed}, {open-eyed}, {vigilant},
             {watchful}]
     2: (of sleep) easily disturbed; "in a light doze"; "a light
        sleeper"; "a restless wakeful night" [syn: {light}]