Wiktionary
d.o.
abbr. (context US English) a http://en.wikipedia.org/wiki/Doctor%20of%20Osteopathic%20Medicine
Wikipedia
D.O. (singer)
Do Kyung-soo (born ), better known by his stage name D.O., is a South Korean singer and actor. He is a member of the South Korean-Chinese boy group EXO and its sub-group EXO-K.