100 entries under observant topic. ×

12
on the ball(expression, adjective, idiom, adverb, keen)
12
on guard(expression, adjective, idiom, adverb, keen)
12
wise(verb, adjective, understanding, keen, sharp)
10
acute(adjective, understanding, strong, keen, sharp)
10
guarded(adjective, adverb, keen, care, sensible)
10
wide-awake(adjective, adverb, keen, sharp, smart)
9
conscious(adjective, understanding, open, keen, sharp)
9
observing(adjective, understanding, keen, sensible, certain)
9
perspicacious(adjective, understanding, keen, bright, perceptive)
8
discerning(adjective, understanding, keen, sharp, smart)
6
knowing(adjective, understanding, keen, sharp, smart)
5
chary(adjective, reasonable, sensible, deliberate, restrained)
5
concentrating(adjective, set, determined, deep, caring)
5
interested(adjective, strong, open, friendly, intense)
5
knowledgeable(adjective, understanding, keen, sharp, smart)
5
on the job(expression, adjective, idiom, keen, sharp)
5
prepared(adjective, care, excited, ready, anxious)
5
rapt(adjective, set, attention, deep, fixed)
5
responsive(adjective, understanding, open, keen, sharp)
5
sensible(adjective, understanding, open, keen, smart)
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APASmart Define. (2016). alert thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/alert/thesaurus/synonyms
ChicagoSmart Define. 2016. "alert thesaurus" https://smartdefine.org/alert/thesaurus/synonyms (accessed September 26, 2026).
HarvardSmart Define 2016, alert thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/alert/thesaurus/synonyms>.
MLASmart Define. "alert thesaurus" 26 February 2016. Web. 26 September 2026. <https://smartdefine.org/alert/thesaurus/synonyms>