[1] : The Collaborative International Dictionary of English v.0.48

observant \observ"ant\, n.
   1. one who observes forms and rules. obs. --hooker.
      1913 webster

   2. a sycophantic servant. obs.
      1913 webster

            silly ducking observants,
            that stretch their duties nicely.     --shak.
      1913 webster

   3. r. c. ch. an observantine.
      1913 webster

[2] : The Collaborative International Dictionary of English v.0.48

observant \observ"ant\, a. l. observans, -anits, p. pr. of
   observare: cf. f. observant. see observe.
   1. taking notice; viewing or noticing attentively; watchful;
      carefully attentive; as, an observant spectator; observant
      habits.
      1913 webster

            wandering from clime to clime observant stray'd.
                                                  --pope.
      1913 webster

   2. submissively attentive; obediently watchful; regardful;
      mindful; obedient to; -- with of, as, to be observant of
      rules.
      1913 webster

            we are told how observant alexander was of his
            master aristotle.                     --sir k.
                                                  digby.
      1913 webster
see also:
observe 

[3] : WordNet (r) 2.0

observant
     adj 1: paying close attention especially to details
     2: quick to notice; showing quick and keen perception syn: observing
     3: of individuals adhering strictly to laws and rules and
        customs; "law-abiding citizens"; "observant of the speed
        limit" syn: law-abiding
see also:
observing law-abiding 

[4] : Moby Thesaurus II by Grady Ward, 1.0

77 moby thesaurus words for "observant":
   argus-eyed, active, advertent, agog, alert, all ears, all eyes,
   assiduous, attentive, aux aguets, awake, aware, careful, compliant,
   concentrated, conforming, conscientious, conscious, constant,
   custodial, deferential, devoted, devout, diligent, duteous,
   dutiful, eagle-eyed, earnest, ethical, faithful, finical,
   finicking, finicky, guarded, hawk-eyed, heedful, intense, intent,
   intentive, keen, keen-eyed, lidless, loyal, meticulous, mindful,
   moral, nice, niggling, obedient, observing, on guard, on the ball,
   on the job, on the lookout, on the watch, open-eared, open-eyed,
   openmouthed, perceptive, practicing, prudent, punctilious,
   punctual, regardful, respectful, scrupulous, sharp, sharp-eyed,
   shrewd, sleepless, thoughtful, true, vigilant, wary, watchful,
   wide awake, with open eyes

Observant >> O Words
Observant, definition of term: Observant
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