- desertion from allegiance, loyalty, duty, or the like; apostasy: His defection to East Germany was regarded as treasonable.
- failure; lack; loss: He was overcome by a sudden defection of courage.
- the act or an instance of defecting
- abandonment of duty, allegiance, principles, etc; backsliding
- another word for defect (def. 1), defect (def. 2)
1540s, “action of failing;” 1550s, “action of deserting a party, leader, etc.” from Latin defectionem (nominative defectio) “desertion, revolt, failure,” noun of action from past participle stem of deficere (see deficient). Originally used often of faith.