The Collaborative International Dictionary of English v.0.48:

Incorrigible \In*cor"ri*gi*ble\, a. [L. incorrigibilis: cf. F.
   incorrigible. See In- not, and Corrigible.]
   Not corrigible; incapable of being corrected or amended; bad
   beyond correction; irreclaimable; as, incorrigible error.
   "Incorrigible fools." --Dryden.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Incorrigible \In*cor"ri*gi*ble\, n.
   One who is incorrigible; a person whose persistent bad
   behavior cannot be changed; especially, a hardened criminal;
   as, the perpetual imprisonment of incorrigibles; incorrigible
   and disruptive children need to be placed in a separate
   classroom.
   [1913 Webster]

WordNet (r) 3.0 (2006):

incorrigible
    adj 1: impervious to correction by punishment [ant:
           corrigible]