passadhi in taiji is 放鬆

 In taiji quan and qigong, passadhi is called

放鬆

fang song, literally 'release [of tension, into a a state of] looseness'

In other words, pacifying/passambhyam  the mental and physical tension we didn't even know we were adding in.

That's why a good taiji teacher, all you hear them say all the time is 'fang song', 'fang song', and the students say, "I am relaxed!", and the teacher keeps telling them 'no you're not."

And even the great masters and grandmasters can take 10 years, 20 years, 50 years, before they really become relaxed.

And for the same reason people can find 2nd jhana  and even first jhana hard to do.

famous taiji grandmaster master chen man ching said it took him 50 years to really understand passsadhi.

http://lucid24.org/sted/7sb/5passaddhi/index.html#calibre_link-18

Once you really get passaddhi and jhana, then any of the internal martial arts that work with qi, taiji, ba gua, xing yi, none of the external differences in appearance, postures, movements matter, they're all working with the same internal energies that you get with with avitakka avicara samadhi.