self-defense

noun

1. the act of defending one’s person when physically attacked, as by countering blows or overcoming an assailant: the art of self-defense.
2. 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.
3. 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).