disloyal

adj

Etymology: From Middle English, from Anglo-Norman desleal, desloial, equivalent to dis- + loyal.

1. Not loyal, without loyalty.

   “1536, Anne Boleyn, letter addressed to Henry VIII from the Tower of London, cited in Edward Herbert, The Life and Raigne of King Henry VIII, London: Thomas Whitaker, 1649, p. 383, Good your Grace, let not any light fancy, or bad Counsel of mine enemies withdraw your Princely favour from me; neither let that stain, that unworthy stain of a disloyall heart towards your good Grace, ever cast so foul a blot on your most dutifull Wife, and the Infant Princesse your daughter […]”

   “[…] Norway himself, With terrible numbers, Assisted by that most disloyal traitor The thane of Cawdor, began a dismal conflict;”