WordWeb Online

1. Carefully observant or attentive; on the lookout for possible danger
   "a policy of wakeful awareness";
   - argus-eyed, open-eyed, vigilant, watchful
    
2. (of sleep) easily disturbed
   "a restless wakeful night";
   - light
    
3. Marked by full consciousness or alertness
   - waking

See also: alert, awake, shallow, watchful

Encyclopedia: Wakeful