What does "out" mean?

Help me, please.
“Mr.Barnes is out sick today”(TOEIC listening part II)
What is the meaning of “out” in this situation? By the way, could you tell me the synonym of it and give me another example of it?
Thanks a lot,
Wishing you have a nice day!

out sick: away from the office/off work because of illness. (out of the wok environment).