To abandon your country, group, or belief system to join the opposing side, usually for political or ideological reasons.
From Latin 'defectus,' past participle of 'deficere' meaning 'to fail' or 'to abandon.' The prefix 'de-' means 'away' and 'ficere' means 'to do,' creating the sense of 'failing to do one's duty.'
Defection became a huge word during the Cold War when spies and athletes from Communist countries would secretly escape to the West—it's still one of international politics' most dramatic moments.
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