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

impeccable \impec"cable\, a. l. impeccabilis; pref. im- not +
   peccare to err, to sin: cf. f. impeccable.
   not liable to sin; exempt from the possibility of doing
   wrong. -- n. one who is impeccable; esp., one of a sect of
   gnostic heretics who asserted their sinlessness.
   1913 webster

         god is infallible, impeccable, and absolutely perfect.
                                                  --p. skelton.
   1913 webster

[2] : WordNet (r) 2.0

impeccable
     adj 1: without fault or error; "faultless logic"; "speaks
            impeccable french"; "timing and technique were
            immaculate"; "an immaculate record" syn: faultless,
             immaculate
     2: not capable of sin
see also:
faultless immaculate 

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

54 moby thesaurus words for "impeccable":
   absolute, accurate, beyond all praise, blameless, chaste, clean,
   correct, defectless, destitute, errorless, exact, exquisite,
   faultless, flawless, ideal, immaculate, impecunious, impoverished,
   indefectible, indefective, indigent, infallible, irreproachable,
   just right, necessitous, needy, nice, peerless, penurious, perfect,
   poverty-stricken, precise, proper, pure, right, sinless, spotless,
   stainless, taintless, unadulterated, unblemished, uncontaminated,
   undefiled, unerring, unfaultable, unflawed, unimpeachable, unmixed,
   unprosperous, unsoiled, unspotted, unsullied, untainted, white

Impeccable >> I Words
Impeccable, definition of term: Impeccable
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