traitorous

adjective2

1. •
   Characteristic of a traitor; disloyal.

   • I tel you true my hart is swolne with wrath, On this same theeuish villain Tamburlain. And of that false Cosroe, my traiterous brother, Would it not grieue a King to be so abus’d? — 1587
2. •
   Constituting treason; treasonable or seditious.