Dictionary.com "martial art
Any of several Asian arts of combat or self-defense, such as aikido, karate, judo, or tae kwon do, usually practiced as sport. Often used in the plural."
OOOOOOoooooooooo. don't tell the boys at my dojo they're doing a sport!!!
IMHO 'Martial' means simply military. 'Art' refers to in depth or philosophical study as opposed to simply 'Skill' or even 'Science'.
So, I have heard it said that Miyamoto Mushashi was the greatest sworsman ever, and Morihei Ueshiba the greatest martial artist. Both fought in wars, and fought well. I find it interesting that both lived long enough to become philosophers. (I don't think 'philosopher' is a bad word, don't tell anybody.)