Disloyal

Part of speech: adjective (a.)

Not loyal; not true to a sovereign or lawful superior, or to the government under which one lives; false where allegiance is due; faithless; as, a subject disloyal to the king; a husband disloyal to his wife. Without a thought disloyal. Mrs. Browning.

Synonyms: Disobedient; faithless; untrue; treacherous; perfidious; dishonest; inconstant; disaffected.