perfidy

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++per·fi·dy /ˈpɜːfədi $ ˈpɜːr-/ noun [uncountable] literary  TRICK/DECEIVEwhen someone is not loyal to another person who trusts them 不忠，背信弃义 SYN treachery

Examples from the Corpus

perfidy• On trips organised for food writers, public perfidy is a popular lament.• Anyway, they've seized on this legal brouhaha as an example of Albion's perfidy, so to speak.• After dinner, they lined the bar, talking loudly about the perfidy of Highlanders and bemoaning their ten-mile, fishless walk.• Young Zuwaya talked with anger and shock, lips and hands trembling, about the perfidy of the Magharba.• When the Seminoles and blacks responded to this perfidy by refusing to cooperate in their removal, Jesup renewed warfare.• But can you live with your perfidy?

per·fi·dy nounChineseSyllable  

Corpus loyal who is not when to them person someone another trusts

perfidy
per‧fi‧dy /ˈpɜːfədi, ˈpɜːfɪdi $ ˈpɜːr-/ noun [uncountable] literary
when someone is not loyal to another person who trusts them
   SYN  treachery

per·fidyBrE /ˈpɜːfədi/ 🔊NAmE /ˈpɜːrfədi/ 🔊 noun [uncountable] (literary) unfair treatment of sb who trusts you 背叛；背信弃义 SYN treachery