The Collaborative International Dictionary of English v.0.48:

Scrupulous \Scru"pu*lous\, a. [L. scrupulosus: cf. F.
   scrupuleux.]
   1. Full of scruples; inclined to scruple; nicely doubtful;
      hesitating to determine or to act, from a fear of
      offending or of doing wrong.
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            Abusing their liberty, to the offense of their weak
            brethren which were scrupulous.       --Hooker.
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   2. Careful; cautious; exact; nice; as, scrupulous abstinence
      from labor; scrupulous performance of duties.
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   3. Given to making objections; captious. [Obs.]
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            Equality of two domestic powers
            Breed scrupulous faction.             --Shak.
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   4. Liable to be doubted; doubtful; nice. [Obs.]
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            The justice of that cause ought to be evident; not
            obscure, not scrupulous.              --Bacon.
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   Syn: Cautious; careful; conscientious; hesitating.
        [1913 Webster] -- Scru"pu*lous*ly, adv. --
        Scru"pu*lous*ness, n.
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WordNet (r) 3.0 (2006):

scrupulous
    adj 1: having scruples; arising from a sense of right and wrong;
           principled; "less scrupulous producers sent bundles that
           were deceptive in appearance" [ant: unscrupulous]
    2: characterized by extreme care and great effort;
       "conscientious application to the work at hand"; "painstaking
       research"; "scrupulous attention to details" [syn:
       conscientious, painstaking, scrupulous]