Source : Webster's Revised Unabridged Dictionary (1913)

Impeccable \Im*pec"ca*ble\, 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.

         God is infallible, impeccable, and absolutely perfect.
                                                  --P. Skelton.

Source : WordNet®

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