[syn: insomniac, sleepless, watchful]
The Collaborative International Dictionary of English v.0.48:
Watchful \Watch"ful\, a.
   Full of watch; vigilant; attentive; careful to observe
   closely; observant; cautious; -- with of before the thing to
   be regulated or guarded; as, to be watchful of one's
   behavior; and with against before the thing to be avoided;
   as, to be watchful against the growth of vicious habits.
   "Many a watchful night." --Shak. "Happy watchful shepherds."
   --Milton.
   [1913 Webster]
         'Twixt prayer and watchful love his heart dividing.
                                                  --Keble.
   [1913 Webster]
   Syn: Vigilant; attentive; cautious; observant; circumspect;
        wakeful; heedful.
        [1913 Webster] -- Watch"ful*ly, adv. --
        Watch"ful*ness, n.
        [1913 Webster]
WordNet (r) 3.0 (2006):
watchful
    adj 1: engaged in or accustomed to close observation; "caught by
           a couple of alert cops"; "alert enough to spot the
           opportunity when it came"; "constantly alert and
           vigilant, like a sentinel on duty" [syn: alert,
           watchful] [ant: unalert, unvigilant, unwatchful]
    2: experiencing or accompanied by sleeplessness; "insomniac old
       people"; "insomniac nights"; "lay sleepless all night";
       "twenty watchful, weary, tedious nights"- Shakespeare [syn:
       insomniac, sleepless, watchful]
Moby Thesaurus II by Grady Ward, 1.0:
74 Moby Thesaurus words for "watchful":
   Argus-eyed, advertent, agog, alert, all ears, all eyes, assiduous,
   attentive, aux aguets, aware, careful, cautious, chary,
   circumspect, concentrated, conscious, covering, custodial,
   defensive, diligent, eagle-eyed, earnest, finical, finicking,
   finicky, fostering, guarded, guardian, guarding, hawk-eyed,
   heedful, immunizing, intense, intent, intentive, keen-eyed,
   lidless, meticulous, mindful, nice, niggling, observant, observing,
   on guard, on the ball, on the job, on the lookout, on the watch,
   open-eared, open-eyed, openmouthed, parental, preventive, prompt,
   prophylactic, protecting, protective, prudent, quick, ready,
   regardful, safeguarding, screening, sharp-eyed, sheltering,
   shielding, sleepless, tutelary, unsleeping, vigilant, wakeful,
   wary, wide-awake, with open eyes