The Collaborative International Dictionary of English v.0.48:

Irrecuperable \Ir`re*cu"per*a*ble\, a. [L. irrecuperabilis: cf.
   OF. irrecuperable. See In- not, and Recuperate.]
   Irrecoverable. -- Ir`re*cu"per*a*bly, adv.
   [1913 Webster]