The Collaborative International Dictionary of English v.0.48:

fedayee \fedayee\ n.; pl. fedayeen. [(1950-1955). Ar.
   fid[=a]'[imac], one who sacrifices himself.]
   a member of an Arab paramilitary organization, predominantly
   Palestinian, which performs commando raids, especially
   against Israel or Israeli targets. Usually used in the
   plural.
   [PJC]

WordNet (r) 3.0 (2006):

fedayeen
    n 1: (plural) Arab guerrillas who operate mainly against Israel