dis·loy·al 
(dĭs-loiəl)
(dĭs-loiəl)adj.
Showing or characterized by a lack of loyalty; not loyal. See Synonyms at faithless.
[Late Middle English, from Old French desloial : des-, dis- + loial, loyal; see LOYAL.]
dis·loyal·ist n.
dis·loyal·ly adv.