faithless applies to any failure to keep a promise or pledge or any breach of allegiance or loyalty.
faithless allies
false stresses the fact of failing to be true in any manner ranging from fickleness to cold treachery.
betrayed by false friends
disloyal implies a lack of complete faithfulness to a friend, cause, leader, or country.
disloyal to their country
traitorous implies either actual treason or a serious betrayal of trust.
traitorous acts punishable by death
treacherous implies readiness to betray trust or confidence.
a treacherous adviser
perfidious adds to faithless the implication of an incapacity for fidelity or reliability.
a perfidious double-crosser
Example Sentences
It would be disloyal to abandon them. we sensed that he was disloyal and would eventually turn on us
Recent Examples on the WebNot on my end, but people who would see me as disloyal, no longer part of the team. Dave Quinn, Peoplemag, 9 Aug. 2022 In 1947, President Harry Truman signed an executive order that gave the executive branch power to investigate and fire any federal employee who was deemed to be disloyal to the country, without having to supply evidence.WIRED, 19 Aug. 2022 There is no such thing as a winner, especially a multi-time winner, that's disloyal. Sydney Bucksbaum, EW.com, 15 July 2022 Maybe this disloyal look happened only for an instant. Lance Eliot, Forbes, 5 July 2022 So strong are the negative associations that the word itself has become a pejorative for someone deceitful or disloyal. Jacob Stern, The Atlantic, 8 July 2022 By the testimony of his own staff, Trump was certainly devious, profane, suspicious, disloyal, unconcerned about morality, principles or the high ideals of public office.Los Angeles Times, 13 June 2022 But feeling overloaded and saying no without feeling guilty or disloyal is a healthy practice. Bryan Robinson, Forbes, 1 June 2022 For others, the author is disloyal to Mr. Trump, breaching trust with him and colleagues still in public life, revealing behavior and remarks thought to have been private. John Bolton, WSJ, 10 May 2022 See More
Word History
Etymology
Middle English, from Anglo-French desleial, desloial, from des- dis- + leal loyal