a. tending to betray; disloyal; faithless
When Caesar realized that Brutus had betrayed him, he reproached his perfidious friend.
Sentence in Classic:
One half of those vain follies were puffed into mine ear by that perfidious Abbot Wolfram, and you may now judge if he is a counsellor to be trusted.
In a few minutes the scuttle was opened, and, bound hand and foot, the still struggling ringleader was shoved up into the air by his perfidious allies, who at once claimed the honour of securing a man who had been fully ripe for murder.
Moby Dick By Herman Melville Context
Any one reading the past history of our city of Florence, and noting what has recently befallen it, will find the French and German nations overflowing with avarice, pride, cruelty, and perfidy, all of which four vices have at divers times wrought much harm to our city.
Discourses on the First Decade of Titus Livius By Niccolo Machiavelli Context
But while I was travelling and getting great riches among these people, my brother was secretly and shockingly murdered through the perfidy of his wicked wife, so that I have no pleasure in being lord of all this wealth.