Source : Webster's Revised Unabridged Dictionary (1913)

Disloyalty \Dis*loy"al*ty\, n. [Pref. dis- + loyalty: cf. OF.
   desloiaut['e], deslealt['e], F. d['e]loyaut['e].]
   Want of loyalty; lack of fidelity; violation of allegiance.

Source : WordNet®

disloyalty
     n : the quality of being disloyal [ant: {loyalty}]