Definition of "perfidiousness" [per•fid•i•ous•ness]

• Unfaithfulness; deceitfulness; perfidy. (noun)

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• "They gave the officers to understand that far from wishing to act as enemies, they were willing to afford the shipwrecked people all the assistance in their power; but these barbarians shewed, on all occasions, a perfidiousness which is peculiar to the inhabitants of these climates; when the brig had sent biscuit on shore, they seized the half of it, and a few moments after, sold it at an exorbitant price, to those from whom they had stolen it."
• "Reagan harped on the perfidiousness of big government every chance he got, no matter the specific occasion."
• "The mismanagement, secrecy and outright graft of the last administration amount to levels of perfidiousness that are tough to match in any administration."