"Nǎocán" is a modern way to say "Báichī", which means idiot. "Nǎocán" is mostly used by young people. "Nǎocán" literally means "disabled brain" in Chinese. You can use "Nǎocán" when you see someone have done something really stupid.
Example:
Your friend: I keep losing wars in Clash of Clans!
You: You are really "Nǎocán"!
