WATCHFUL

alert, watchful

(adjective) 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”

insomniac, sleepless, watchful

(adjective) experiencing or accompanied by sleeplessness; “insomniac old people”; “insomniac nights”; “lay sleepless all night”; “twenty watchful, weary, tedious nights”- Shakespeare

Source: WordNet® 3.1

Etymology

Adjective

watchful (comparative more watchful, superlative most watchful)

observant, vigilant and aware

Source: Wiktionary

Watch"ful, a.

Definition: 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. 'Twixt prayer and watchful love his heart dividing. Keble.

Syn.

– Vigilant; attentive; cautious; observant; circumspect; wakeful; heedful.

– Watch"ful*ly, adv.

– Watch"ful*ness, n.

Source: Webster’s Unabridged Dictionary 1913 Edition