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.