What is the "Xuanwu rejecting corpse" in Feng Shui? Someone who knows can help me ~

The so-called "Xuanwu refused the corpse" came from the book "Burial Book" written by Guo Pu, a geomantic master in Jin Dynasty. "Xuanwu ChuiShou, rosefinch dance, tsing lung wind, white tiger bent down. If the situation is reversed, it should be against the law. Therefore, the tiger squat is called a corpse, and the dragon squat is called a jealous Lord. Those who don't hang down in Xuanwu refuse to die, and Suzaku doesn't dance. " If the back hill doesn't hold its head high, it's called "Xuanwu refuses the corpse". In layman's terms, the back hill behind the acupoint looks ugly, especially when it is far away from the acupoint and heartless, it is generally not suitable for burial. I don't know if you understand.