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.
The island opens up about American role in training troops for self-defense.
From The Wall Street Journal ● Aug. 5, 2026
And Judge Krause wrote that “circulation data reveals only how many units” of a weapon that companies have “pumped into the marketplace,” not how many people have used that weapon for self-defense.
From Slate ● Jul. 24, 2026
Homeland Security officials say the agents fired in self-defense.
From The Wall Street Journal ● Jul. 17, 2026
After some past shootings by immigration officers, including those in Minneapolis of Alex Pretti and Renee Good, federal officials’ accounts that the officers acted in self-defense have been contradicted by video evidence.
From Los Angeles Times ● Jul. 10, 2026
In our case it was simply a legitimate form of self-defense.
From "Long Walk to Freedom" by Nelson Mandela
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
