self-defense n1 : the use of force to defend oneself
2 : an affirmative defense (as to a murder charge) alleging that the defendant used force necessarily to protect himself or herself because of a reasonable belief that the other party intended to inflict great bodily harm or death see also justification
Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.