中东 - "Middle East" or "Eastern China"?
In all the news reports in Mainland China, "中东" refers to Middle East. This can be seen as a convention -- as a native speaker, if I hear "中东", I will definately think of the Middle East. You can take a look at the Wikipedia Page of 中东, and the Baidu Baike Page of 中东. Only one meaning is referred on both pages -- Middle East.
If anyone wants to refer to Eastern China, they will say "中国东部（地区）". The dictionary lists Eastern China for "中东", which looks like a result from translation software... So the dictionary makes a mistake.


I don't know if 中东 has any other meaning in Taiwan, Hong Kong, etc. But when I search for 中东, I also noticed that in Japanese, the combination of these two Characters also refers to Middle East.