the act or method of defending or protecting oneself; the capability of resisting attack
ex: We do not always have the luxury of choice when timing our attack and defense.我们经常极少有机会选择何时攻击或防御。
But jelly fish usually use it as a defense against predators.
政治：the Ministry of Defense 国防部
法律：come to one’s defense 为某人辩护
1. The tannins are part of the defense mechanism that is essential to longevity.
2. Well, what is his defense of slavery?
3. He briefed me about his earlier work at the the Ministry of Defense.