retrogradation
/ˌretrəʊgreɪˈdeɪʃən/noun
mass noun
1- Astronomy & Astrology the apparent temporary reverse motion of a planet (from east to west), resulting from the relative orbital progress of the earth and the planet【天文, 占星】（行星的）逆行。
1.1
- the orbiting or rotation of a planet or planetary satellite in a reverse direction from that normal in the solar system（行星或行星卫星的）逆行。
词源
mid 16th cent.: from late Latin retrogradation- （see RETRO-, GRADATION）.