Tai chi is an abbreviation of tai chi chuan. Other spellings commonly used - t'ai chi, taiji or taijiquan.
It is pronounced 'tie jee'.
Tai chi is usually translated as 'great ultimate' or 'supreme ultimate' but this does not explain what the words mean.'
Great ultimate' is a reference to the yin/yang process of dynamic balancing.
Chuan means fist, boxing, or martial art.
Tai chi chuan means yin/yang boxing or supreme ultimate fist.