Martial arts are arts of combat or self-defense.
The gymnasium on board the Galaxy-class starship had martial arts areas. (TNG: "Clues", "Second Chances")
Tuvok had extensive training in the martial arts of many Alpha Quadrant cultures. He knew of over 94 ways of killing someone using only a finger, a hand, or a foot. (VOY: "Meld")
Jadzia Dax was an expert in Klingon martial arts. (DS9: "Facets")