Definition of "perfidy" [per•fi•dy]

• Deliberate breach of faith; calculated violation of trust; treachery: "the fink, whose perfidy was equaled only by his gall” ( Gilbert Millstein). (noun)
• The act or an instance of treachery. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "But much as she loved England she was very loud in denouncing what she called the perfidy of the mother to the brightest of her children."
• "One that routinely engages in perfidy, intentionally targets civilians, uses hospitals, schools and mosques to hide and fire rockets, transports its soldiers and material using ambulances marked with the red crescent, refuses to abide by a unified command structure, refuses to wear distinctive insignia, .... is not comparable to a “freedom fighter” in any respect except the trivial."
• "The day the nadir of his perfidy is brought to light, he will effectively have put the lives of hundreds of thousands — maybe even millions of Americans and more worrisome to him — American Interests (“Cha-CHING!”) in exponentially greater jeopardy than before."