self-defense
Americannoun
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the act of defending one's person when physically attacked, as by countering blows or overcoming an assailant.
the art of self-defense.
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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.
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an act or instance of defending or protecting one's own interests, property, ideas, etc., as by argument or strategy.
Other Word Forms
Etymology
Origin of self-defense
First recorded in 1645–55
Explanation
When you protect yourself forcefully against an attack, that's self-defense. If you kicked a dog that tried to bite you, you don't need to feel bad: it was self-defense. The act of defending yourself, protecting yourself from being physically harmed, is self-defense. You can take a class to learn tactics of self-defense; many martial arts can be used this way, to fend off an attacker. Self-defense is also a legal right — by law, people can use "reasonable force" to defend their own lives. Self-defense was originally a sporting term, first used in fencing and then in boxing.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Reyes believes the pair agitated the dog, who reacted in self-defense.
From Los Angeles Times ● Oct. 13, 2026
Reynano López 46, an avocado farmer, starts his morning shift with the self-defense militia.
From Los Angeles Times ● Sep. 6, 2026
Having sworn never to be taken back to slavery alive—or to let that happen to anyone else—he had organized an armed self-defense force of black neighbors to fend off slave catchers.
From The Wall Street Journal ● Sep. 2, 2026
In Byrd and Roberts’ case, the state insists it arose in seconds, during the same chaotic burst of gunfire that even the judge agrees began as lawful self-defense.
From Slate ● Aug. 11, 2026
Not the best weapon for self-defense, but it would serve in a pinch.
From "The City Beautiful" by Aden Polydoros
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
