The Collaborative International Dictionary of English v.0.48:

Punctual \Punc"tu*al\, a. [F. ponctuel (cf. Sp. puntual, It.
   puntuale), from L. punctum point. See Point.]
   1. Consisting in a point; limited to a point; unextended.
      [R.] "This punctual spot." --Milton.
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            The theory of the punctual existence of the soul. --
                                                  Krauth.
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   2. Observant of nice points; punctilious; precise.
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            Punctual to tediousness in all that he relates. --
                                                  Bp. Burnet.
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            So much on punctual niceties they stand. --C. Pitt.
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   3. Appearing or done at, or adhering exactly to, a regular or
      an appointed time; precise; prompt; as, a punctual man; a
      punctual payment. "The race of the undeviating and
      punctual sun." --Cowper.
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            These sharp strokes [of a pendulum], with their
            inexorably steady intersections, so agree with our
            successive thoughts that they seem like the punctual
            stops counting off our very souls into the past. --
                                                  J. Martineau.
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WordNet (r) 3.0 (2006):

punctual
    adj 1: acting or arriving or performed exactly at the time
           appointed; "she expected guests to be punctual at meals";
           "he is not a particularly punctual person"; "punctual
           payment" [ant: unpunctual]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "punctual":
   accurate, active, alert, apt, attentive, careful, close, compliant,
   conforming, conscientious, conscionable, constant, correct,
   critical, decisive, delicate, demanding, detailed, devoted, devout,
   duteous, dutiful, exact, exacting, exigent, expeditious, exquisite,
   faithful, fastidious, fine, finical, finicking, finicky, fussy,
   heedful, immediate, instant, instantaneous, loyal, meticulous,
   mindful, minute, narrow, nice, observant, on the dot, on time,
   overconscientious, overscrupulous, painstaking, particular,
   practicing, precise, precisianistic, precisionistic, prompt,
   punctilious, quick, ready, refined, regardful, religious, rigid,
   rigorous, scrupulous, scrutinizing, speedy, strict, subtle,
   summary, swift, tender-conscienced, timely, true