"Cào" is one of the most popular bad words in Chinese. "Cào" literally means "f**k" in Chinese but its real meaning is more like "f**k you". You can use "Cào" alone or you can combine with other Chinese bad words. It is considered pretty rude when you use this word. However, it is one of the most important word that you must know when you travel to China.
Example:
Someone: "Cào"! Get out of here!
You: "Cào"! I am leaving now!