TMA means 'tradional martial art'. Like all terms, it is somewhat arbitrary, but a rough definition might be: "an art that places a high value on preserving the specific techniques, principles, and (sometimes) training methods of a past master, or esteemed group of martial artist's/warriors". Also, often tied to training in TMA is learning the history of the culture that the art developed in, as well as cultural specific protocol, and etiquette, sometimes based on a now passed time period.

Hope that helps.

"Seek not to follow in the footsteps of the men of old; seek what they sought."