- the act of defending one’s person when physically attacked, as by countering blows or overcoming an assailant: the art of self-defense.
- a claim or plea that the use of force or injuring or killing another was necessary in defending one’s own person from physical attack: He shot the man who was trying to stab him and pleaded self-defense at the murder trial.
- an act or instance of defending or protecting one’s own interests, property, ideas, etc., as by argument or strategy.
n.1650s, “act of defending oneself,” first attested in Hobbes, from self- + defense. In sports sense, first with reference to fencing (1728), then boxing (1820s).