Watchful 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.

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Taxonomy
Merriam-Webster Online Dictionary, ful, Dictionary, danger, webster, Word Games, Webster Online Dictionary with audio pronunciations, watchfulness, thesaurus, glossary, english, language, ESL, Search, adjective, 15th century, sleep, sleeplessness.

Defination from the web:
watchful from the Merriam-Webster Online Dictionary with audio pronunciations, thesaurus, Word of the Day, and word games. ... synonyms watchful, vigilant, wide-awake, alert mean being on the lookout especially for danger or opportunity. ...