名詞 precession:

1. the motion of a spinning body (as a top) in which it wobbles so that the axis of rotation sweeps out a cone
2. the act of preceding in time or order or rank (as in a ceremony)
   同義詞：precedence, precedency

pre.ces.sion

n.（名詞）
The act or state of preceding; precedence.
先行：向前運動的行為或狀態(tài)；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.
【物理學(xué)】 進動：當(dāng)受到外力作用時旋轉(zhuǎn)體軸的運動，如旋轉(zhuǎn)陀螺般的搖擺
Astronomy
【天文學(xué)】
Precession of the equinoxes.
分點歲差
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.
歲差：地球中軸繞黃道極的緩慢旋轉(zhuǎn)，主要由于太陽、月亮和其它星體對地球赤道降起帶的重力作用而造成

來源：
Late Latin praecessiô praecessiôn-
后期拉丁語 praecessiô praecessiôn-
from Latin praecessus [past participle of] praecôdere [to go before] * see precede
源自 拉丁語 praecessus [] praecôdere的過去分詞 [回到從前] *參見 precede

【引伸】
preces.sional
adj.（形容詞）