falsehearted

from The Collaborative International Dictionary of English v.0.48

False-hearted \False"-heart`ed\, a.
   Hollow or unsound at the core; treacherous; deceitful;
   perfidious. --Bacon. -- {False"-heart`ed*ness}, n. --Bp.
   Stillingfleet.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

50 Moby Thesaurus words for "falsehearted":
      Machiavellian, ambidextrous, artful, calculating, chiseling,
      collusive, covinous, crafty, crooked, cunning, deceitful,
      dishonest, disingenuous, double, double-dealing, double-faced,
      double-minded, double-tongued, doublehearted, duplicitous,
      faithless, false, false-principled, finagling, forsworn,
      fraudulent, furtive, guileful, indirect, insidious, insincere,
      perfidious, perjured, scheming, sharp, shifty, slippery, sneaky,
      surreptitious, treacherous, trickish, tricky, two-faced, uncandid,
      underhand, underhanded, unfrank, unsincere, untruthful, wily