Not that I know of. Tai chi is not only a form of meditation, but a form of martial arts...and martial arts. There is nothing in Druidic circles that really compares. Druids do meditate though, and they also believe in an energy force (what Asians call 'chi' or 'ki')...but I don't know of a specific separate practice attributed to Druids concerning it. Not to say that they wouldn't incorporate it into their beliefs, I just don't know of anything like that that is specific to Druidism.