p.o.'d is a very informal American way of writing pissed off, which means very angry — not a little annoyed, but fed up and sharp about it. Writers used the letters so they did not have to print the rude word. You may still see it in older US newspapers, comics, or casual messages; younger people more often just write pissed or pissed off. It is slang, a bit dated on the page, and too rough for school essays or talking to a teacher. Use it only if you are copying how an American character talks.

氣炸了（美式粗話 pissed off 的書面縮寫）