jus·ti·fi·ca·tion /ˌjəs-tə-fə-'kā-shən/ n
1: the act or an instance of justifying
2: something that justifies; specif: a legally sufficient reason or cause (as self-defense) for an act that would otherwise be criminal or tortious
3: the affirmative defense of having a legally sufficient justification compare excuse
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.