Definition of "perfidious"

TRINCULO (speaking about Caliban): By this light, a most perfidious and drunken / monster: when his god's asleep, he'll rob his bottle.

1610–1611 (date written), William Shakespeare, “The Tempest”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act II, scene ii]

The perfidious Ricimer soon became dissatisfied with Anthe'mius, and raised the standard of revolt.

1851, Oliver Goldsmith, “ch. 26”, in William C. Taylor, editor, Dr. Goldsmith's History of Rome

[S]he knew Huntly for the ambitious traitor he was, a man peculiarly perfidious and self-seeking.

1905, Andrew Lang, “ch. 14”, in John Knox and the Reformation

When the Nazis branded Feininger a "degenerate artist" in 1937, he left 54 paintings for safekeeping with a Bauhaus friend named Hermann Klumpp. After the war, and for the rest of Feininger's life, the perfidious Klumpp refused to give them back.

2005 June 21, “Art: The Velocipede of Modernism”, in Time‎, archived from the original on 12 November 2011

Enraged, the 2010 Nobel literature laureate thundered that he was “flabbergasted to learn that this kind of gossip can find its way into a respectable publication such as the Book Review” - a “slanderous and perfidious” instance of the convergence of posh and pop that his book inveighs against.

2015 August 28, John Dugdale, “Mario Vargas Llosa, Hola! and the shallow reading of a review”, in The Guardian‎