precession

n. 先行, 优先
【化】 进动; 旋进

形容词:precessional 

pre.ces.sion

n.（名词）
The act or state of preceding; precedence.
先行：向前运动的行为或状态；先行
Physics The motion of the axis of a spinning body, such as the wobble of a spinning top, when there is an external force acting on the axis.
【物理学】 进动：当受到外力作用时旋转体轴的运动，如旋转陀螺般的摇摆
Astronomy
【天文学】
Precession of the equinoxes.
分点岁差
A slow gyration of Earth`s axis around the pole of the ecliptic, caused mainly by the gravitational pull of the sun, moon, and other planets on Earth`s equatorial bulge.
岁差：地球中轴绕黄道极的缓慢旋转，主要由于太阳、月亮和其它星体对地球赤道降起带的重力作用而造成

来源：
Late Latin praecessiô praecessiôn-
后期拉丁语 praecessiô praecessiôn-
from Latin praecessus [past participle of] praecôdere [to go before] * see precede
源自 拉丁语 praecessus [] praecôdere的过去分词 [回到从前] *参见 precede

【引伸】
preces.sional
adj.（形容词）