The Collaborative International Dictionary of English v.0.48:

Irredeemable \Ir`re*deem"a*ble\, a.
   Not redeemable; that can not be redeemed; not payable in gold
   or silver, as a bond; -- used especially of such government
   notes, issued as currency, as are not convertible into coin
   at the pleasure of the holder. -- Ir`re*deem"a*ble*ness,
   adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

irredeemable
    adj 1: insusceptible of reform; "vicious irreclaimable boys";
           "irredeemable sinners" [syn: irreclaimable,
           irredeemable, unredeemable, unreformable]
    2: (of paper money) not convertible into coin at the pleasure of
       the holder