A person or thing that defects, especially someone who abandons a country, organization, or cause to join another side.
From Latin 'defectus' (failure, deficiency) plus English agent suffix '-er.' The word traces through 'defect' which meant to fail or fall away, evolving to mean abandoning one's allegiance.
During the Cold War, 'defectors' were major news stories—famous cases like Yuri Nosenko and Klaus Fuchs show how the word became tied to political betrayal, but it literally just means 'someone who fails [to stay loyal].'
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