Treason/ˈtriːzn/ Definition 1 of 2Pro Tip 1/3Personal Betrayal Treason can imply a deep personal betrayal, not just a legal offense. His treason was felt deeply by his longtime mentor. Pro Tip 2/3Historical Use Historically, treason involved aiding enemies or threatening a ruler's life. Knights who betrayed their king were guilty of treason. Pro Tip 3/3Grave Accusation Being accused of treason is very serious and scandalous. The spy denied the allegations of treason against her.