defection
nounUK /dɪˈfɛkʃən/
US /dɪˈfɛkʃən/
The act of leaving your own group or country to join another one.
The spy's defection to the other side shocked everyone.
OTHER MEANINGS
2. The loss of something because it is not perfect or complete.
The defection in the crystal made it break easily.
3. A failure to do what you promised or were supposed to do.
His defection from the team left them short of players.
4. The act of leaving a political party to join another.
The politician's defection changed the balance of power.