a person who defects from a cause, country, alliance, etc.
Origin: 1655–65; < L dēfector renegade, rebel, equiv. to dēfec- (var. s. of dēficere to become disaffected, revolt, lit., to fail; see defect) + -tor-tor
To disown allegiance to one's country and take up residence in another: a Soviet citizen who defected to Israel.
To abandon a position or association, often to join an opposing group: defected from the party over the issue of free trade.
[Middle English, from Latin dēfectus, failure, want, from past participle of dēficere, to desert, be wanting : dē-, de- + facere, to do; see dhē- in Indo-European roots.] de·fec'tion n., de·fec'tor n.
[di-fek-ter] 
tər