perfidious
Breaking sworn oaths
Perfidious means treacherous or disloyal, especially through deliberate betrayal of trust.
The word carries a literary or formal tone and implies calculated deception rather than mere unreliability: perfidious allies, a perfidious act.
The phrase perfidious Albion is a traditional epithet accusing England of diplomatic treachery.
Untrustworthy, lacking loyalty
- disloyalUntrue to commitments
- inconstantProne to fluctuation
- fickleErratically disloyal in affection
- false-heartedDeceptive in affection
untrue · adulterous · two-timing · cheating · straying · oath-breaking · promise-breaking · forsworn
Deliberately deceptive in nature
- dishonestInclined to deceive
- falseNot matching reality
- untrustworthyNot deserving of confidence
- insincereFeigning belief or feeling
guileful · dissembling · underhanded · deceptive · scheming · sly · crafty · cunning
Deliberate violation of trust
- backstabbingCovert betrayal of trust
- disloyaltyBreach of allegiance
- double-crossTreacherous deception of partner
- treasonBetraying one's nation
sedition · subversion · defection · apostasy · breach · falseness · turncoat · quisling
faithless
Untrustworthy, lacking loyalty
- disloyalUntrue to commitments
- inconstantProne to fluctuation
- fickleErratically disloyal in affection
false-hearted · untrue · adulterous · two-timing · cheating · straying · oath-breaking · promise-breaking · forsworn · recreant
duplicitous
Deliberately deceptive in nature
- dishonestInclined to deceive
- falseNot matching reality
- untrustworthyNot deserving of confidence
insincere · guileful · dissembling · underhanded · deceptive · scheming · sly · crafty · cunning · two-faced
treachery
Deliberate violation of trust
- backstabbingCovert betrayal of trust
- disloyaltyBreach of allegiance
- double-crossTreacherous deception of partner
treason · sedition · subversion · defection · apostasy · breach · falseness · turncoat · quisling · fifth columnist
- fancy wordsgrandiloquent, magniloquent, sesquipedalian, pulchritudinous, tintinnabulation
- betrayerstraitor, betrayer, backstabber, turncoat, double-crosser
- wickedevil, wicked, villainous, malicious, sinister
perfidioustrustworthy
Worthy of confidence
honorable · honest · faithful · reliable · dependable