adverb
- in a way that involves deliberate betrayal of trust; treacherously
Usage: formal
Examples
- The spy perfidiously sold state secrets to enemy agents.
- She perfidiously abandoned her allies when they needed her most.
- The general perfidiously switched sides during the crucial battle.
- He perfidiously broke his oath of loyalty to the king.
- The business partner perfidiously stole the company’s trade secrets.
- The diplomat perfidiously violated the terms of the peace treaty.