Is Ninjutsu a martial art? What is a Martial art?

Many people are now stating that Ninjutsu isn't a martial art, if they are saying its a way of life and more than a martial art then in some cases I would agree, who am I to say if or if not they live their lives by the code of the ninja I sometimes have used ninjutsu strategy outside the dojo of course, that's what its for. However some are saying (in documentaries, online and in publications) that Ninjutsu is a military art or a set of military strategies. Well in my humble they need to look at what "Martial" means because in my dictionary it says:-

martial
adjective \ˈmär-shəl\
Definition of MARTIAL
1: of, relating to, or suited for war or a warrior
2: relating to an army or to military life
3: experienced in or inclined to war : warlike.

so if Martial means "war" or "military" then shouldn't ALL martial arts be military, war or combat strategies to qualify the name Martial Art?

Just my humble opinion, other opinions are just as valid. As always - do your research and ask your instructor (AYI).