怎么回事

1. • what's the matter?
2. • what's going on?
3. • how could that be?
4. • how did that come about?
5. • what's it all about?

Character by character

• 怎(zěn)how
• 么(me)suffix, used to form interrogative 什么 shénme, what?, indefinite 这么 zhème thus, etc
• 回(huí)Hui ethnic group
• 事(shì)matter