The Collaborative International Dictionary of English v.0.48:

Improbity \Im*prob"i*ty\, n. [L. improbitas; pref. im- not +
   probitas probity: cf. F. improbit['e].]
   Lack of probity; lack of integrity or rectitude; dishonesty.
   [1913 Webster]

         Persons . . . cast out for notorious improbity.
                                                  --Hooker.
   Improficience

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "improbity":
   Machiavellianism, ambidexterity, artifice, bad faith, cunning,
   deceitfulness, dishonesty, double-dealing, doubleness,
   doubleness of heart, duplicity, faithlessness, falseheartedness,
   falseness, low cunning, treachery, two-facedness, wile