perfidiousness

== English == === Etymology === From perfidious + -ness. === Noun === perfidiousness (usually uncountable, plural perfidiousnesses) (rare) Unfaithfulness; deceitfulness; perfidy. Synonyms: double-dealing, treachery, treacherousness; see also Thesaurus:betrayal ==== Related terms ==== perfidious perfidiously === References === Noah Webster (1828), “perfidiousness”, in An American Dictionary of the English Language: […], volume II (J–Z), New York, N.Y.: […] S. Converse; printed by Hezekiah Howe […], →OCLC. “perfidiousness”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC. “perfidiousness”, in Dictionary.com Unabridged, Dictionary.com, LLC, 1995–present.