The Collaborative International Dictionary of English v.0.48:

irridenta \irridenta\, irridentism \irridentism\, irridentist
\irridentist\n.
   See irredenta, irredentism, irredentist.
   [PJC]

WordNet (r) 3.0 (2006):

irridentism
    n 1: the doctrine that irredenta should be controlled by the
         country to which they are ethnically or historically
         related [syn: irredentism, irridentism]