The Collaborative International Dictionary of English v.0.48:

irreclaimable \ir`re*claim"a*ble\, a.
   Incapable of being reclaimed. --Addison. --
   ir`re*claim"a*bly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

irreclaimable
    adj 1: insusceptible of reform; "vicious irreclaimable boys";
           "irredeemable sinners" [syn: irreclaimable,
           irredeemable, unredeemable, unreformable]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "irreclaimable":
   beyond recall, beyond remedy, cureless, gone, graceless,
   immedicable, incorrigible, incurable, inoperable, irrecoverable,
   irredeemable, irreformable, irremediable, irreparable,
   irretrievable, irreversible, irrevocable, lost, past hope,
   past praying for, remediless, ruined, shriftless, terminal, undone,
   unmitigable, unredeemable, unregenerate, unrelievable, unsalvable,
   unsalvageable