1. the act of abandoning a group, cause, or allegiance in favor of an opposing one

Examples

• The senator’s defection to the opposing party shocked his supporters.
• Several high-ranking officials announced their defection from the regime.
• The spy’s defection provided valuable intelligence to enemy forces.
• His defection from the team came at a crucial moment in the season.
• The defection of key members weakened the organization significantly.
• She was accused of defection after joining the rival company.