The Collaborative International Dictionary of English v.0.48:

Incorruptible \In`cor*rupt"i*ble\, a. [L. incorruptibilis: cf.
   F. incorruptible. See In- not, and Corrupt.]
   [1913 Webster]
   1. Not corruptible; incapable of corruption, decay, or
      dissolution; as, gold is incorruptible.
      [1913 Webster]

            Our bodies shall be changed into incorruptible and
            immortal substances.                  --Wake.
      [1913 Webster]

   2. Incapable of being bribed or morally corrupted; inflexibly
      just and upright.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Incorruptible \In`cor*rupt"i*ble\, n. (Eccl. Hist.)
   One of a religious sect which arose in Alexandria, in the
   reign of the Emperor Justinian, and which believed that the
   body of Christ was incorruptible, and that he suffered
   hunger, thirst, pain, only in appearance.
   [1913 Webster]

WordNet (r) 3.0 (2006):

incorruptible
    adj 1: incapable of being morally corrupted; "incorruptible
           judges are the backbone of the society"

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "incorruptible":
   amaranthine, deathless, dependable, embalmed, ever-fresh,
   everlasting, fadeless, faithworthy, frozen, immortal, imperishable,
   impregnable, indelible, indestructible, ineffaceable, ineradicable,
   inexpugnable, inextinguishable, invincible, inviolable,
   invulnerable, irrefragable, never-dying, nonperishable, proven,
   quenchless, reliable, responsible, straight, sure, tested,
   to be trusted, tried, tried and true, true, trustable, trustworthy,
   trusty, undampable, undestroyable, undying, unfading, unfalse,
   unperfidious, unquenchable, untreacherous