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.
      [1913 Webster]

            Abusing their liberty, to the offense of their weak
            brethren which were scrupulous.       --Hooker.
      [1913 Webster]

   2. Careful; cautious; exact; nice; as, scrupulous abstinence
      from labor; scrupulous performance of duties.
      [1913 Webster]

   3. Given to making objections; captious. [Obs.]
      [1913 Webster]

            Equality of two domestic powers
            Breed scrupulous faction.             --Shak.
      [1913 Webster]

   4. Liable to be doubted; doubtful; nice. [Obs.]
      [1913 Webster]

            The justice of that cause ought to be evident; not
            obscure, not scrupulous.              --Bacon.
      [1913 Webster]

   Syn: Cautious; careful; conscientious; hesitating.
        [1913 Webster] -- Scru"pu*lous*ly, adv. --
        Scru"pu*lous*ness, n.
        [1913 Webster]

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]

Moby Thesaurus II by Grady Ward, 1.0:

155 Moby Thesaurus words for "scrupulous":
   Pyrrhonic, accurate, active, agnostic, analyze, attentive, bashful,
   boggling, canvass, careful, case, cautious, censorious, check over,
   check up, choicy, choosy, close, comb, compliant, con, conforming,
   conscientious, conscionable, consider, constant, contemplate,
   correct, critical, deferential, delicate, demanding, demurring,
   detailed, devoted, devout, diffident, dig into, discriminating,
   discriminative, dissect, distrustful, doubtful, doubting, dubious,
   duteous, dutiful, ethical, exact, exacting, examine, exigent,
   exquisite, eye, eyeball, fair-minded, faithful, faltering,
   fastidious, fine, finical, finicking, finicky, from Missouri,
   fussy, heedful, hesitant, hesitating, high-minded, honest,
   honorable, in doubt, inspect, just, leery, look over, loyal,
   methodical, meticulous, mindful, minute, mistrustful, mistrusting,
   modest, moral, narrow, neat, nice, obedient, observant, orderly,
   overconscientious, overlook, overscrupulous, painstaking,
   particular, penetrate, perfectionistic, perlustrate, peruse, picky,
   pierce, pore over, practicing, precious, precise, precisian,
   precisianistic, precisionist, precisionistic, priggish, principled,
   probe, prudish, punctilious, punctual, puristic, puritanic,
   qualmish, questioning, refined, regardful, religious, respectful,
   right, righteous, rigid, rigorous, scan, scrutinize, scrutinizing,
   selective, sensitive, severe, shrinking, shy, skeptical, squeamish,
   stickling, strict, study, subtle, survey, suspecting, suspicious,
   tender-conscienced, true, uncertain, untrusting, upstanding, vet,
   view, wary, watch, weigh