What does ghost water mean?

"Ghost water" is a traditional Chinese word, which often appears in classical Chinese. It means "water used to sprinkle on the altar during sacrifice".

According to allusions, in ancient times people sprinkled clean water on the altar to show their respect, but at that time some people used unclean water for some reasons, so they were considered as "ghost water" because it was unclean and unlucky.

Later, the word "ghost water" became a word to describe unclean, polluted, evil and disgusting water. For example, there is a description of "ghosts boiling" in A Dream of Red Mansions, which describes the desolate scene and evil breath.

Therefore, generally speaking, the word "ghost water" is often used in literary works to describe some ominous scenes or things.