Definition of "traitor"

My Lord of Hereford here whom you call King, / Is a foule traitour to proud Herefords King, / And if you crowne him let me propheſie, / The bloud of Engliſh ſhall manure the ground, / And future ages groane for this foule act, [...]

1595 December 9 (first known performance), [William Shakespeare], The Tragedie of King Richard the Second. […] (First Quarto), London: […] Valentine Simmes for Androw Wise, […], published 1597, [Act IV, scene i]

Yes, that was Vice President Spiro Agnew commemorating the "loyalty" of literal traitors. But what can you really expect from a man whose name rearranged spells "grow a penis."

2017 October 8, “Confederacy” (14:45 from the start), in Last Week Tonight with John Oliver‎, season 4, episode 26, John Oliver (actor), via HBO

It took you two weeksTo go off and date herGuess you didn't cheatBut you're still, you're still a traitorYeah, you're still a traitor

2021, Olivia Rodrigo, Dan Nigro (lyrics and music), “Traitor”, in Sour‎, performed by Olivia Rodrigo

to find a subject staid and wiseAlready half turn'd traitor by surprise

1735, Alexander Pope, “The Second Satire of Dr. John Donne”, in The Works of Mr. Alexander Pope, volume II, London: […] J. Wright, for Lawton Gilliver […]