The Collaborative International Dictionary of English v.0.48:

double cross \double cross\, double-cross \double-cross\n.
   teh act of double-crossing; the betrayal or swindling of a
   collaborator or colleague.

   Syn: cross, betray.
        [PJC]

The Collaborative International Dictionary of English v.0.48:

double cross \double cross\, double-cross \double-cross\v. t.
   to betray or swindle (a colleague); to promise (a
   collaborator) one thing and to treacherously do another, to
   the detriment of the collaborator.

   Syn: cross, betray.
        [PJC] double cross

WordNet (r) 3.0 (2006):

double cross
    n 1: an act of betrayal; "he gave us the old double cross"; "I
         could no longer tolerate his impudent double-crossing"
         [syn: double cross, double-crossing]
    v 1: betray by double-dealing